What are you thinking of asking him?
is it "Will you go out with me?"
or is it "Would you like to go out for a drink / pictures / cinema?"
You could easily ask if he would like to do something like go to the cinema or a drink. You don't have to say it's a date. It's just two people going for a drink / watch a film and having a nice time. If it leads to anything more then that's great!
If it's any inspiration I asked out the man who is now my husband 5 and half years ago.
I actually said "Would you like to go to the theatre with me sometime?"
Unfortunately I mumbled and as we were in a pub at the time and the music was quite loud he actually heard "Would you like to sleep with me sometime?"
He said yes - I think he was a bit disappointed when he got theatre tickets!