1.) Start by playing an ADC who can farm Safely.
are both great examples to start with. Remember that bot is a harass-heavy lane, and one of the primary ways to STOP an ADC from getting fed is to harass them to the point of where they are too scared to CS. Find a way to CS safely.
2.) Do everything in your power to get as many of the minions as possible. Use abilities, don't shy away from it.
3.) Take pure damage runes, and buy dorans to start, your initial damage is really, really important for early game CS. Doubly so if you think you are having trouble.
4.) Practice makes perfect, the more you do it, the easier it will come, and the less you will have to think about it. Once you get to that level, you can start harassing enemy champions while simultaneously maintaining your CS.