You need a good star chart such as Sky Atlass 2000 Deluxe ($100) or download each chart from the following link:
http://www.asahi-net.or.jp/~zs3t-tk/...5/atlas_85.htm I prefer the charts without constellation lines since there are no lines in the sky.
Then you need to familiarise yourself with what is where and when. A planisphere will tell you what where and when (expecpt for planets). At the moment Scorpius & Sagittarius (centre of our galaxy) is high in the evening and there are countless of fine objects to look at.
If you can find Scorpius follow it from Antares (bright orange star) to the end of its tail where you may spot a faint 'smudge' which is M7, an open cluster. Your local light pollution will play a big part here if you see this or not.
Now, find the tail of Scorpius and M7 on your charts and use this as you reference point to search for M8 & M20 (Lagoon & Trifid).
I like to think of M8 & M20 as being within the steam coming from the spout of the teapot (Sagittairius). Of course a bright city location will rule out seeing any of what I just described.
If you do have a light polluted sky you will need to star hop from the brightest stars in the region and always cross check with your map to ensure you are looking at the correct star. Look at star patterns on the map and see if you can find them in the sky. (A Telrad helps here to star hop). Also have a look at the following Telrad charts. The one for M7 also shows M8 at the top of the page.
http://www.utahskies.org/deepskyIndex.shtml
I like the scale of Sky Atlas 2000 and have the original deluxe version which goes to mag. 8. The new one goes to mag 8.5. The deluxe version is in colour and is very easy to read.
to IIS.
I recently purchased a Baader OIII filter from erick on these forums, and it's made a big difference to my viewing of nebulas in my light polluted skies with my 8". I've been looking at M20 (Trifid Nebula) lately, and without the filter, all I see is what looks to be a star cluster with maybe the faintest hint of nebulosity. Put the filter on and WOW, where did all that come from? 
