The cost of a harness can range from $15-$250 dollars depending on the quality of the material and craftsmanship. If you’re just looking to have one night of fun, there are lots of comfortable, inexpensive products to choose from (usually nylon and rubber), but if you’re looking to strap it on frequently, buying a better-made, more-durable harness is a worthwhile investment (leather is the most durable).
What kind/shape/size of cock are you going to want to use in the harness?
Most harnesses have a ring of some sorts that holds the dildo/cock in place. Some rings are interchangeable for any size, but others only fit specific sized toys. Also, harnesses made out of cloth aren’t going to hold up a heavy cock as well as a leather one would. Knowing what size of a cock you want to put in your harness is an important step in figuring out what kind of harness you’ll need. (Get more tips and style recommendations in Strap On the Fun?.)
During the Purchase
Don’t be afraid to try the product on in the store. A good sex shop will have products on display, and you can also call a shop to have them help with your choice. If you’re purchasing online, make sure you get a measuring tape and measure your body where the harness is going to hit.
Most manufacturers have sizing guidelines, so be sure to follow them. A good fit makes all the difference with a harness.
Before Sex
There is always awkwardness in trying something new, so having a sense of humor is the best advice I can give when it comes to strap-on sex, and really, sex in general. You’re going to feel like a pubescent boy, so just go with it: run around the house doing "the wiggle dance," shove your cock between couch cushions, (consensually) put it in your partner’s ear ... whatever helps you to get used to it and feel comfortable.
Get your giggles out as much as possible now and you’ll feel more comfortable when it’s time to put the harness into action.
Getting Down to Business
Start simple, don’t go for the full Kama Sutra in one night. Missionary style can be surprisingly exhausting and difficult to maneuver. Try switching to something like doggy style or cowgirl, where it’s easier to see what you’re doing.
If you’re the one receiving penetration, it’s important to guide the harness wearer. Let them know what they are and aren’t doing right, and remember that this is new to them, so have some patience with your pleasure.
Harness Care and Cleaning
It is very important to keep your harness clean to avoid bacterial infections and other STIs. Cloth harnesses can be thrown in the washing machine, but leather harnesses are a bit trickier to clean.
Good luck - and happy humping! (Afraid to try a strap-on? Check out 7 Big, Fat Misconceptions About Strap-Ons.)