While many enjoy OWO, some prefer oral sex with a condom (otherwise known as covered oral) to help minimise the risks of transmitting STIs. STIs can still be passed during oral, so safety is very important. Many say that they prefer oral without because it feels better, but oral with a condom can still be very enjoyable, as being safe in knowledge that you will not contract something from your partner can help you relax and allow you to enjoy the sensation of your penis being in another's mouth.
Just because your cock is covered doesn't mean you can be lazy when it comes to hygiene. Cleaning your manhood is still vital, even with covered oral, so make sure you give him the attention he needs so that later he can get the attention he deserves. Soap and warm water are the most useful tools at your disposal, and make sure you take more than a minute to wash your member. Pulling back the foreskin and cleaning the entire area (not just the shaft) can ensure you get a good time later on.
Part of the fun of covered oral is actually putting the condom on. You could do this yourself, or your partner may wish to try a different way. Some enjoy putting it on with their mouth, and for men this can be extremely pleasurable. If you want to try it, make the suggestion to your partner. Some people feel more comfortable securing the condom with their hands, so it is worth checking.
With covered oral, the possibilities for where and how you finish are endless. Some will be more than happy for you to cum in their mouth (with condom) while they perform oral on you, while others may prefer you to give them a facial, or to cum on their tits or ass. Let your partner know what you'd prefer so that, when the time comes, they know what to expect. If you have chosen to cum in mouth (with condom), then just lie back and enjoy. For those wanting to cum on their partner's face, tits, or ass, give them plenty of warning when you are getting close. This will give them time to take the condom off and give you control so you can masturbate over their body in the way that you want.