1) How can i determine which lane to go to? When i played Warlock i had someone tell me to go mid, but in my other matches i just kinda winged it.
You should ask. It comes down to team composition and where everyone else is going. Here is a quick run down from the perspective of Radiant:
Top AKA Short Lane AKA Suicide Lane: Support, semi carry
Mid: Ganker/initiator/Farmer
Bottom AKA Long Lane AKA Safe Lane: Support, hard carry
As Warlock, you have two different roles. You can be Support. Or you can be Initiator (with your Golem). In the game where you went mid, you were playing Initiator.
Another useful nomenclature is "1-5 roles", which rank heroes based on their farm priority, with 1 being the highest and who gets most farm, and 5 being the lowest/ward bitch. Using that, laning is typically:
Top: 3, 4
Mid: 2
Bottom: 1, 5
When a jungle is present:
Top: 4
Mid: 2/3
Bottom: 1, 5
Jungle: 2/3
In a defensive trilane:
Top: 3
Mid: 2
Bottom: 1, 4, 5
In an offensive trilane:
Top: 1/2, 4, 5
Mid: 1/2
Bottom: 3
2) Is there a hotkey to instantly snap camera focus back to my hero? In league and dawngate it's spacebar. I couldn't seem to find which option it'd be in the keybindings. I kept getting disoriented in fights because i'd accidentally switch to my warlock's pet or my spiderling and then try to get back to my hero and end up running around uselessly.
There's a binding under Unit Actions called Select Hero. Double tapping whatever you bind that too will center the camera over your hero. Generally, double tapping some sort of unit selection snaps your camera to it.