Cait has one of the longest attack ranges among AD carries, which allows he to both poke, and farm from a distance without allowing the enemy laners much of a chance to counter her. I personally do not play ADC, however, I enjoy playing Cait from time to time because it's so easy to farm with her. I can hit about 90 cs in 11 minutes with her because of her range and her Q ability.
Some tips would be this:
1) Focus on farming instead of harassing. Cait's ability to farm is very high in comparison to a lot of other ADC.
2) Last hit minions well. Try to use just your auto attack to last hit things,but do not be afraid to use your Q ability to last hit a few minions as well!
3) Try to have all 3 traps in your lane at one time. And place them in places where the enemy jungler will come from if your support doesn't have a ward.
4) Always make sure to have enough mana for your net and a trap just in-case you need to run from a gank. The net will allow you to get away, and the trap can be used to disrupt people from chasing your or your support.
5) Build Infinity Edge first, especially if you're new to the role of ADC. This allows you to do damage in team fights and increases your farming ability. After you get the hang of the role you can experiment with other items.
6) Consider buying a hunter's machete and 5 potions to start. I really like doing this on cait because it allows you to last hit like crazy. Your range will allow you to evade a lot of the harass, and the recent buffs to movement speed (and your displacement from your net) will allow you to escape early ganks quite well. However, this is strictly for a farm lane, and is something I only do in normal games.
I hope I was able to help you with this. I'd recommend going onto solomid.net and looking at some live streams of adc players. Guides help too, you can look on solomid.net, leaguecraft.com, lolking.net, or mobafire.com. All of their top rated guides are pretty good, read them all to see how different people play.