I don't have very many places to fish but I go to a lake close to where I live most of the time. It is very grassy and has thick cover both submerged and above the water. What kind of lure and what tequnique should I use to catch lunker bass? Any advice and tips will be helpful.

well, I'd try a plastic of some sort.  twitch it around in the grass so the bass see it movin around, without a weighter on it, or c-rig it if the grass is in the water so the plastic floats above the grass.

like I hear alot of people saying, move it slow.

if the grass is along the shore, toss the lure in front of the grass and pull it along the shoreline.  

if the water is warm enough, cast a spinner/buzzbait in front of the grass along the shoreline.  maybe cast it right at the edge of the grass (do the same with worm) and have it bumpin the grass as it comes down the shoreline.

hope I could help some.  

For the Lunker use BIG baits sumthin big attracts big fish sound like the lake has a lot of structure so try diff techniques: jig, trickworm, jerkbait, and spinnerbait mainly is what I would throw into the water in your situation.

Use a rat or take a 7" plastic worm and thread the hook so that it is rigged texas style but the hook sits in the middle not towards the head. Most of your bites the bass will hit it in the middle of the worm and it also helps the bait sit ontop of the grass and sink parallel instead of nose down.

Thanks for all the help. I will try some of those tequniques. I will let you know if I catch any lunkers.

in dense structure like that, heavy jigs at 3/4 ounce, 10" worms with heavy weight, try a topwater frog... spinnerbaits and plastics around the timber.  the heavy weight is to get the bait down in the grass instead of keeping it on top.  although the topwater frogs will work wonders... and if the grass isn't totally out of the water, you could even try a buzzbait or a pop-r

Lots of grass, I like it all the time.  Especially during the hot summer months.  I really like to RAT fish the top of the muck or moss.  The reason...it doesn't matter whether it's hot, day or night, the bass will seek it out for cover.  So I would always fish on top of the muck or moss with a RAT.  You can also use soft plastics, like I've seen mentioned here.  If there are pockets in between, then pitch soft baits in the pockets.  Have fun, because it can be heart stopping fishing a RAT!

A long texas rigged worm, 10 inches or better.

well me pesonaly i would try a 6-8 inch texas style rig