I have some tips I wish people would have told me when I was starting to play with polymer clay. Here they are:
1- If you want to remove lint, dirt, color from light pieces of clay, rub them with acetone. Also use gloves while you work with them. I recommend sterilized gloves.Make sure that you keep a spray with alcohol around and napkins to always wipe everything after using other colors. Also, if you don't like using gloves, you can simply get a piece of white clay and roll it on your hand to get everything on it.
2 - Uncooked polymer clay will deteriorate some types of plastic so make sure that you keep it away.
3 - Always store clay that you don't use in plastic foil.
4 - If clay hardens, there's no need for quick mix, you can just use some hand cream or liquid clay. Cut it in small pieces, pour some liquid clay on them and mix them together.
5 - You can mix brands of polymer clay to achieve harder clay Premo is harder while Fimo Soft or translucent clays are softer. You can mix them together to achieve the firmness you want.
6 - Babywipes are always good for cleaning things.
7 - If you don't want moonies on your clay projects (small bubbles that form when playing with transparent-ish clay) you should gradually heat them before reaching the right temperature for baking. Don't preheat the oven.
8 - Buy bigger chunks of polymer clay. It's cheaper. Start with red, yellow, blue, white and black. Mix them together to create other colors.
9 - You can make your own sculpting tools, there is no need to buy most of them. Just search for the sculpting tool you need and make it out of polymer clay.
10 - Invest in a pasta machine if you want to have smooth and precise finished products.