Many condoms have reservoirs for this. Gently squeeze excess air from the sides of the condom as it is unrolled onto the penis. Do not force out excess air by pushing from the top down after the condom has been placed. This can stretch and weaken the latex. Sadly, women still have to make sure their partners use them.
Women are the ones who risk conceiving and who are most at risk from fluid exchange.
Experts agree that condom use is a touchy but essential subject to broach. Timing is critical. Nor do you want to seem like you've been hoarding a couple hundred of them. Introduce the topic well ahead in humorous conversation, and wait for a reaction. But don't fool yourself thinking that everything will work out if you haven't brought up the topic during dinner or out on the town.