One of the most intimidating things for new pilots — or pilots who rarely fly into controlled airports — is communicating with air traffic control. A video from the AviationGuys covers the basics of talking to air traffic control, with real-life examples from their own flying.
Clearance is the first controller in C and B airports, D airports you ground acts as clearance and ground. But the first contact is to get clearance instructions. Most often you do not need to talk to ground again after your runup if the runup is near or at the runway holding point. Monitor ground but switch to tower because you will need clearance to takeoff from the tower.
In all cases you are always responsible for your own collision avoidance under VFR conditions. In a line up and wait situation you MUST still verify that no traffic is on approach before taking the runway and holding.
There is no reporting point under VFR. You just need to contact approach or tower before entering D, C, B airspace. For B airspace you must hear “cleared to enter” for the others you must have two-way radio contact which includes ATC referencing your tail number.
A great resource is http://www.liveatc.net