Clothing: Leave the denim at home. First cotton can kill out on the trail if it gets wet, and second it is down right heavy. Wool, wool blend and synthetics are going to offer you just as much if not more protection and will weigh in a lot less. If you are going out for just a few days consider limiting the change of clothes or not taking a change at all (with exception to socks and underwear). Although you should never under estimate the elements, evaluate what you have. Do you really need that polar fleece vest and a sweatshirt to sleep in? Are four different shirts really needed on this trip?
Food: One word - repackage. You don't need to take the entire bottle of Log Cabin Syrup and the box of Crusteaz with you to make pancakes for two. Measure out only what you will use and repackage it in reusable containers. Reusable containers that hold from one to four ounces of dry or liquid food goods can be found just about anywhere, including Wal-Mart for under $4. Peanut butter can be put in squeeze tubes, which can be bought in sets of two for under $3. Dry foods can be put in small plastic bags. Take a black marker and write the cooking directions on the plastic bag so you don't have to take the directions with you. Even pre-packaged dried foods can be put in plastic bags to conserve room. Not only will you save weight you carry in but also reduce the amount of trash you have to carry out.
Niceties Of Life: You can convince yourself all you want how important it is to bring that sitting pad, the coffee pot, a small radio, a six pack of beer, an axe, folding cot or any other number of things you might take with you to make life on the trail easier. Never eliminate an essential; trimming weight off your pack by eliminating your rain gear or first aid kit isn't a sound strategy. However leaving your rain pants behind when the forecast is sunny and leaving the snakebite kit at home when you're hiking in the North Cascades of Washington are subtle ways of cutting ounces. A stump will make an adequate chair, you can make instant coffee in a cup, you don't need a radio, you're just going to have to carry out those beer bottles, and you're not suppose to burn anything you can't break with your hands anyway.
The Pack: People tend to fill up their backpacks even if it is too large for the planned trip. If you are going on a weekend trip you will probably want to leave the 5,000 cubic inch pack at home. If you are very active in the outdoors you may need a couple of packs to meet your various needs depending on the activity you plan.
If you spend some time going through your gear you can find a number of ways to strip off the pounds you are carrying. You might have to invest some money updating some pieces of gear, but the investment on saving wear and tear on your body is priceless, and it will bring you more enjoyment when you're in the great outdoors.