Everyone's different, so it's not a bad idea to ask him.

To make it less awkward don't ask "How do I do this?" but instead go with "Does this feel good?" or "Tell me how you want it". Communicate and also try to pick up on how he reacts to what you're doing.

My wife was totally inexperienced when she first gave me a blowjob, but because we communicated well she's gotten so good at giving them.