Questions about tarps...

[rodar y rodar]

With a simple floorless tarp setup, what prevents water from running down the side of your tarp to the ground and then right into your sleeping gear?

I`ve seen references to sewing bug netting around the sides of a tarp.  Then what do you do to keep the free edge of the netting down?  Just let it hang?  Bury it?  Weights or stakes?  Does it need to be sealed tightly against the ground all the way in order to be effective?

[Slim]

Have a look at Backpackinglight. They are big time tarp promoters and have many articles about them. Also any number of books including Ray Jardines and BPL's Beyond Backpacking have good chapters on tarping.

[12wheels]

The key to comfortably using a tarp is to choose the right camping site.  Scope out the terrain and avoid areas which might flood or where water might pool.   

The Backpackinglight website is an excellent resource and Whiteblaze.net is also worth checking out. 

Here are a couple basic articles which are also useful:
http://members.tripod.com/halbertri/tarps.htm
http://www.outdooridiots.com/features/200606/pitchingatarp/pitchingatarp.asp
http://hikinghq.net/gear/tarp.html

Quite a few tarp campers use bivys as added protection from the elements and to keep the bugs out.  Here's a real basic but functional design which you can purchase or make:
http://www.sixmoondesigns.com/ultralight/myo_Meteor.asp

[rodar y rodar]

Thanks for the links.  Some I haven`t run into yet, others I`ve looked at but I have to admit I didn`t actually study them.  A bivy AND a tarp?  I thought most folks used one or the other.  Wouldn`t packing both of them kind of negate the weight advantage over a small tent?

[12wheels]

The Six Moons Bivy weighs 7 oz and a silnylon 6 x 8 tarp or 5x 7 ft poncho will weigh around 9 oz.  Stakes and cord will add another 2-3 oz so the combo is equal to or lighter than most single person tents with bug netting.   The bivy cost $125 from Six Moons and a silnylon tarp or ponch will run $50-65.  Stakes and cord cost around $7-10.   

The materials to build a copy of that bivy will cost around $50-60 and a 5x7 or 8ft silnylon tarp only uses $30-35 worth of fabric.   Learn to sew and save some serious cash. 

[rodar y rodar]

Yeah, my two man tent is pretty light, but that combo still beats it by a long shot and solidly beats the single version of the same tent.  I believe you about learning to sew too- not just to save money, but to be able to get sewn gear EXACTLY how I want it rather than the closest commercial product.  I`ve been reading up more on the tarps- if I still have questions after a better study I`ll post back.