You think you've placed a dot on your nails with a dotting pen, but it comes out teardrop-shaped, touches its neighbor, or changes size from dot to dot. Before adding more designs, try drawing one dot at a time on a practice tip. A dot being small and a dot having a clean outline are two separate things to check.
Here, we use a nail dotting pen with a ball-shaped tip and draw dots on a practice tip fixed to a stand. Use paint that is compatible with the tools you have, and do not treat drying or curing and finishing steps for gel and polish as the same process.
1. Separate size from outline, and check the tip and the paint

First, look at the dot you drew from almost directly above. Tell apart whether it is round but the wrong size, whether it trails a tail to one side, or whether the outline is blurred and has joined its neighbor. If you sum it up as "I couldn't make it small," it becomes harder to choose what to change next.
What you want to check is the outer edge of the dot. Tilt the tip slightly so you don't mistake a white patch of reflected light for the outline. However, if you view only one dot from an angle its shape looks stretched, so return to the same viewing direction when you compare. Judge the size of the dot separately from the gloss of its surface.
Dotting pens come with ball tips of different sizes. Even if there is a ball on both ends, do not assume the two sides are the same size; check which one you used. Look at the tip, not the color or pattern of the handle, and decide which side to use before you start practicing.
Also check that no lump of the previous color or dirt remains on the tip. If something covers the shape of the ball, do not try to fix the shape by pressure alone. Follow the tool's instructions for care. If you are bothered by scratches or deformation on the surface, avoid sanding it back into shape on your own.
Next, make sure the paint and the tool can be used together. Gel, polish, and nail art paint are handled differently. Even if you can't draw a dot, don't change the viscosity by mixing in water, remover, or another gel; use the specified method only where adjustment is permitted.
The goal of practice is not to finish a whole design from the start. First aim for this state: "place one dot, and still be able to judge its shape after lifting the pen." Jotting down the tip and type of paint you used makes it easier to return to the next comparison.
2. Fix the tip in place and adjust the amount picked up on the tip

Fix the practice tip to a compatible stand and make sure it doesn't wobble and that the surface you will draw on is visible. Support the wrist or the little-finger side of your working hand in a comfortable position, and move containers and unneeded tools out of the area your pen tip will travel. If you keep holding the tip with one hand, the movement of the dot and the movement of the stand get mixed up.
If you apply a base color, prepare it as specified until you reach the stage where the next color can be layered. Check polish drying and gel curing separately. Even if you place dots on a surface that still drags, you are not practicing just comparing the amount on the pen.
If the paint may be portioned out, put the necessary amount on a compatible palette and close the container. Avoid holding an open container in one hand while trying to draw with the other. Prepare a palette that suits the material and a place where you can set the tool down without it rolling.
Pick up a small amount of paint on the ball tip and look at how it adheres from the side. Don't dip broadly up to the base of the handle, and don't carry a blob that is about to drip; first place one dot on a separate practice spot to check the amount. We do not fix the right amount as a set number of drops.
When you want to reduce the amount, adjust the tip with a method suited to the paint and the tool, and then pick up paint again. Do not press the ball hard to squash out the excess paint. It is also important not to treat how far the color spreads on the palette as the same thing as the size of the dot placed on the tip.
If the portioned-out material starts to dry or a lump remains on the tip, do not continue practicing in that state. Check the working conditions and care for the products you have, and take a break. Also avoid mixing leftovers back into the original material unless you have confirmed they can be returned to the container.
3. Touch one spot lightly and lift the pen without dragging it sideways

Decide on one position to draw, and adjust the tip stand so that the tip of the ball is visible. At first, try on an empty spot away from the edge, such as near the center of the tip. Don't bend your wrist unnaturally to reach the edge of the curved surface; change the direction of the stand and then support your hand again.
Carry the tip to the target position and touch it lightly rather than pressing in hard. Then lift the pen in the direction that releases contact, without dragging it sideways from that position. When practicing placing a dot, the point to check is not to add the sideways sliding motion you would use when drawing a line.
After you lift the pen, don't go back to the same dot right away; look at the outline. If it trailed a tail, think back on whether your hand moved sideways while lifting, or whether the tip was catching on the base. Don't decide the cause from the shape alone; recall the actual movement of your hand as well.
If you want to make the dot smaller and keep poking the tip into it or tapping around it, you lose track of the first contact. Leave the first dot as a reference and draw the next one in a separate place. Separate this from techniques for drawing large dots; here you practice the motion of placing a dot with a single contact.
If your hand trembles, rather than hurrying to lift the pen, review the support of your stand and hand. Instead of gripping the handle hard, place the stand at a distance where you can see the tip, and return your shoulder and wrist to a relaxed posture. When you change how you support your hand, try one dot without changing the amount at the same time.
Do not compare a dot right after placing it with one after the specified drying or curing process is finished. Follow the label for the waiting time and process the material needs, and do not shorten the curing time on your own to check the shape. Also do not touch uncured gel with your finger to tidy up a dot.
4. In a different spot, compare the amount and tip size in order

Place the next dot in an empty spot that does not touch the previous dot. If you crowd the dots together, it becomes hard to tell whether a dot lost its shape or joined its neighbor's paint. First compare the outline of a single dot, and practice evening out the spacing afterward as a separate step.
If the shape is round but too large, use the same tip and slightly review the amount you pick up for the next dot. Keep the base, the paint, and the support of your hand the same, and narrow what you change down to one thing. If the amount is too small and the dot comes out chipped, do not call it a success just because it is small; check the amount at which the outline holds together.
If reviewing the amount still does not bring you close to the target size, check whether there is a compatible smaller ball tip. When comparing by changing the tip, do not also switch the paint to a different color. Placing two dots drawn with the same material side by side makes it easier to focus on outline and size.
If a tail appears, don't just increase or decrease the amount; check with the next dot whether you could lift the pen from the same position without shifting sideways. If the outline spreads, go back and check the base and the preparation of the material as well. Avoid blaming every flaw on pressure, or assuming the ball size alone will fix it.
If the size changes as you keep placing dots, note down when you picked up paint again too. Distinguish whether you picked up paint each time or placed several dots from the same load. Don't set a fixed correct answer such as re-picking every so many dots; look at the condition with the paint and tip you have.
When removing a failed dot, check the tools that can be used on that material and tip, and the stage at which it may be touched. If it bleeds into other dots, do not keep wiping forcibly; move to a new practice tip. Do not transfer material to your natural nails or skin for the purpose of correcting.
5. Review the outline, then finish and care for your tools

After drawing a few dots, put the pen down and look at the tip again from the same direction and in the same light. Separate checking the outer edge of each dot from checking the spacing as a pattern. Looking first at the shape of the dots, then at their sizes, and finally at their placement makes it easier to sort out what you want to fix.
Even if you can see round outlines, if one dot is joined to its neighbor, review the spacing of the placement next time. If it is a design in which you deliberately varied the sizes, there is no need to make them all the same size. Check separately the conditions you wanted to match and the conditions you wanted to change.
In your practice notes, record the actions you took, such as "used the smaller ball," "picked up paint again before one dot," or "moved sideways while lifting." Rather than rushing to judgments like "I improved" or "it lasts longer," writing down which dots led you to think so gives you material to choose the next step.
For finishing, check the instructions for each paint. For gel, read the compatible lamp, the curing conditions, and whether a finishing product is needed as a set, and do not shorten them because the dots are small. For polish too, follow the conditions for layering the next coat, and do not repeatedly trace over dots that haven't dried with a finishing brush.
After use, remove the residue from the dotting pen in a way that suits that tool and the paint. Also look at the joint between the ball and the handle, and do not store it with dirt left on it. Do not soak it in a solvent you haven't confirmed is usable or scrape off lumps with a blade; go back to the care instructions.
For your next practice, choose one task from the dots you left this time and start again. If you also want to check preparation before painting, check nail basics against the process for the products you have. Separating the motion of placing a dot from the motion of drawing a line makes clear what you are checking at hand.