Inject in your delt with a 1" needle. Just hit it straight on in the middle of the medial delt. It's easier than you think. Don't worry about bubbles. Just make sure you are not in a vein.
Solid advice!
I personally like quads...they are easier to reach and keep steady....more likely to hit a bad spot....but its a LOT easier to aspirate on a quad then a delt.
I would pick a glute before a delt....but delts are easy once you do them...most people are more at ease with them.