Blocking light from getting into the light path of the telescope through the scope or into the eyepiece through your eye makes an appreciable difference in the contrast of your viewing, even (or perhaps, especially) under light polluted conditions.  Keep light from getting into the focuser around an excessively short upper end of your scope, and put a baffle in place behind the primary mirror cell-- both will make a huge difference!   Using an aggressively sized eyepiece cup or the unfashionable "head shroud" helps to cut ambient light at the eyepiece, but both can be problematic in terms of promoting fogging or frosting of the glass.  Hint:  if you want to buy "after market" eyepiece cups to replace worn out ones or get more light blockage, Orion Telescope (http://www.telescope.com/shopping/product/detailmain.jsp?itemID=170&itemType=PRODUCT&RS=1&keyword=rubber) and Edmund Scientific (http://scientificsonline.com/Product.asp_Q_pn_E_3053890) both sell aftermarket cups, and Edmund stocks sizes appropriate for larger 2" eyepieces.  However, these are pricey (up to $25 each); you can actually buy the cheaper Orion models (three for $10), cut them apart and crazy glue them together to make a custom fit for any eyepiece. (A three pack of 1.25" Orion models will make two Nagler 31-sized eyecups.)

Blocking Environmental Light (streetlights)

Here is something I resorted to after years of putting up with a streetlight some 50 feet away from my observing site that casts enough direct illumination for me to read the fine print on star charts by.  I ended up making a type of "backboard" that could be raised on a telescoping pole the ~18 ft and placed atop the light fixture, to block only the light coming in my direction.  I only put this up when I am trying deep sky observing.  The typical caveats apply-- I wouldn't try this if there electrical lines in the vicinity (we actually have underground utility lines), and I don't know what the legal situtation is with respect to the utility company or motorists.  Still, it works!

The Common Tarp: Headlight Glare stopper, privacy screen, and wind break

As mentioned in my observing report on the G.W. "Helipad", headlight glare and visits from white-light toting locals are the biggest impediments to observing at that site.  This time I opted to set up farther to one edge of the narrow ridge, which helped to get my scope out of line of sight of the headlights.  The greatest improvement, however, came from an inspiration I got while shopping at "America's astronomy store"-- aka Walmart.  There I'd discovered some 12 ft. square dining tarps complete with poles, lines, and stakes for $10.  I'd picked up two, and this was my chance to try them out.  Instead of pitching five ~6+ foot long poles, I combined their sections to yield three poles of 8+ foot length.  I used these to elevate the edge of the tarp closest to my scope, and staked the opposite end of the tarp directly to the ground (with a little line to let it raise up 6" or so in the wind).  This made a great headlight barrier against passing cars, and I think shielded me from direct view enough that the folks who stopped and got out of their cars didn't wander over out of curiosity.  Pitched with the low side towards the wind, I suspect this same setup would be a reasonably effective windbreak, too!  It took about 10-15 minutes to set a tarp up, and the hardest part was finding ground that wasn't so rocky it bent the stakes before they got deep enough to hold!  At this price, I could see bringing three or four of these along on my next foray to the Pad...

Eyepiece cups are a near essential accessory when observing from light polluted environments

The parts of the low-tech steetlight shield

Raising the shield-- I look and feel a bit like a lamplighter of old when doing this!

Glare screen erected against headlights