Coming from the other side of things... I'm a support main, and it can be quite difficult not knowing what my adc wants to do if it's someone I've never played with before. And as I play most of my matches either alone, or with friends in other lanes, that's most of my adcs. I try to ask in champ select what kind of playstyle the adc has, as far as how aggro they want to be, and pings and such are always a good tool for when to look to go in for a trade.
It never hurts to let your support know before the match starts that you want to focus on farming, or that you want to try and go for early kills. Or even just to ask them what they might like to do as well. The only warning I will say, is if you use pings to let your support know that you want to go in, and you are waiting on them to initiate, don't forget that they are keeping track of many things before they go in. A good support will be watching for where the enemy jungler is, health and mana bars, ability cooldowns, summoner spell cooldowns, the numbers of creeps in the wave, how close they are to leveling up vs how close the enemy might be to leveling up, any missing enemy laners, etc. I don't always have time to explain those things to my adc, but if he wants me to go in and I don't, it's because I have a darn good reason for it.