Style
All harnesses have a standard 2" opening to hold a dildo. In some this opening is a hole, in others a rubber or metal O-ring held against a backing pad. One advantage of removable O-ring harnesses is that the ring can be replaced with smaller or larger rings to accommodate any size of toy.There are two basic styles of harness, jock and g-string. Jock style harnesses have two straps that wrap around your legs; this makes them very stable and comfortable. G-style harnesses have just one strap that passes between your legs, and lets you feel the motion of the dildo more. G harnesses can also give great clit stimulation, and are handy for holding a toy (or two!) inside the wearer. The G-style harness is a good harness to choose when using a double dildo such as the Feeldoe or the Nexus.
For something completely different, consider a thigh harness. These simple rigs wrap around one thigh (or shin, or waist, or chair, etc.), and can provide an amazing variation on the usual bump and grind.
Fasteners
The great buckle/D-ring debate rages on … D-rings offer quick adjustment at the tug of a strap, a great feature for those who like to change dildos mid-play, or for a harness you plan to share. Buckles, on the other hand, can take a bit of fiddling with, but once they're on they stay put—and they look damn sexy.Material
Sexy as thigh-high boots, tough as baseball mitts, practical like a tool belt, leather is the top choice for many harness aficionados. It's durable and resilient, and it molds to your body with use, so it only gets comfier with age. The weight/thickness of the leather will determine the life span of your rig. Soft leather is cozy but doesn't last as long as hard leather that will need some working in.PETA rejoice! Vinyl and rubber are two spiffy, cruelty-free alternatives to leather. Both are durable, comfortable and hip. Vinyl and rubber can be sweaty, especially in the summer, but that's not necessarily a bad thing.
Ready-to-wear nylon may be less durable than leather or rubber, but it's definitely more affordable, instantly comfy, and washable to boot. Nylon may be a good first choice for a harness that's inexpensive and easy to use.