Tip #1: Do NOT use MS Paint. Photofiltre and Photoshop are better for pro Skin makers. I would say if you have Photofiltre, or Photoshop and you are starting out, try using them for editing. For beginners, use MC Skinedit. It’s much easier, and has a nice interface.
Tip #2: Do NOT use a lot of colors, or neon colors. It hurts the eyes and looks bad. I would say, just don't do it.
Tip #3: Do NOT make a skin that has hundreds of skins made for it. (Ex. Yoshi, Mario, TMNT) ,unless it's every different.
Tip #4: If you are making a skin of a video game, or movie person; Use Google or something to bring up the image, don't draw from memory.
Tip #5: If you cannot Hand draw or so called "Mouse draw" Use other people's skins and edit them. (Remeber Credit!) Simple as it needs to be.
Tip #6: Take your time. A skin you are going to upload or use should look nice so you will want to keep that skin or have others download it.
Tip #7: Use the burn tool (If you’re looking for Minecraft looks) in MC Skinedit (Or Dodge and Sponge tools Photoshop)
Tip #8: Use hats to your advantage, such as using it as a normal hat, ears, or even noses.
Tip #9: Use fitting colors. Using fitting colors makes your skin look nice. (Ex. Dark night with dark colors)
Tip #10: Use the skin you made to see if it fits in Minecraft. Because the skin doesn’t appear exactly what it does with the lighting of Minecraft.
Tip #11: When looking in game, dose the armor cover the eyes? If it does, then fix it.
Tip #12: Remember, Hats go under armor. So make sure the armor makes sense with the hair and ears.
Tip #13: Be creative with your skins. If you want a dragon with eyes on its side, do so. It looks neat and different.
Tip #14: If none of this works for you, you can request skins, but you don't get a whole lot of control with what you get.
Tip #15: Good luck, have fun.