The easiest way is to wrap a sling around the beam using either a choker or a basket hitch. A basket hitch is stronger, but a choker won't slide. Personally, I'd say go with a choker to keep your sling in once place. If your sling is long enough, you can wrap it completely around the beam and finish with a basket hitch to get both the strength of a basket and the compression of a choker. If you use a basket hitch of any kind, make sure the sling angle is over 45 degrees. Much less than that and you'll start to really compromise the strength of your sling.

You can just go from the sling around the beam straight to a carabiner attached to the trapeze. If you need extra length to adjust the height a bit you can either use a longer strap in a choker hitch or attach a second sling to the one wrapped around the beam. It's really a matter of personal preference. I generally try to use the least amount of parts necessary to get an elegant solution, but there are situations where a couple extra pieces can make for a stronger rig overall.

If you're not familiar with the different types of hitches, there's a pretty straight forward diagram here: www.westernequipmentltd.com/slin...1.jpg There's a short intro to sling rigging that explains a bit of the math behind calculating working load limits here: www.fdlake.com/rig-slng.html

2000lbs should be ok for a sling used for trapeze. A choker hitch will decrease the load by about 70-80%, so factor that in. If you bounce around a lot in your act, get a stronger sling just to be on the safe side. If not, 2000lbs should be fine.

If you're performing or training daily with a lot of drops and generally putting a lot of wear on your equipment, I'd say change your gear every six months to a year. Softer gear like ropes and slings are more susceptible to abrasion, so make sure you either put it through a sheath or put a blanket under it whenever it goes over an edge (like the edge of a beam). That'll give you some extra life. From my experience, metal bits can be replaced every year or so. It's a fairly aggressive retirement plan, but I prefer to put in some extra time and money to buy peace of mind. Your mileage may vary, and it's all very dependent on what kind of gear you're using and how you're using it. The best way is to make your own retirement plan. Inspect your gear weekly, before rigging in a new venue, and after you take it down. Keep a log of when you buy new equipment and what you find with each inspection. Eventually you'll get a pretty good idea of when you're replacing what and can build a schedule that fits your gear and your performance style.