What about your odds and ends like bug repellent, camera, notepad, travel alarm clock (who takes a clock camping) the deck of cards and those spare socks? Find a free spot in one of the easily accessed side pockets and stuff them in there. Make sure critical needs like rain gear, warmer clothes, sun screen, bug repellant, water and food can be easily accessed without taking your pack off. This is especially true of your water supply, as a water bottle in your pack is not going to keep you well hydrated on the trail.
On the subject of water bottles, store your water bottles in plastic bags. The cheap bags you get at the grocery store work fine. As you hike during the day water bottles stored in your pack can weep from condensation, soaking your gear (learned this one the hard way at Yellowstone National Park one year).
If you're doing specialized camping say in the winter time, most packs have loops for ice axes and other accessory gear. Make sure that warm gear is easily accessible as well as the stove. Sure it takes some time to fire it up every few hours and then wait a while for it to cool, but your body will appreciate the warm liquid during your breaks.
Avoid packing small items by themselves in larger compartments. Movement and gravity will make that pocket knife move to the bottom of the pocket it is stowed in.
Make sure you balance your load. Don't have too much extra weight on one side or the other. If you are carrying heavy or bulky objects make sure they are closer to your back and your natural center of gravity. Pack your load top heavy and you will be staring at the ground all day. Pack your load bottom heavy and your shoulder straps will dig into you. Load too heavy to the left or right, and the imbalanced load will hurt your shoulders, hips and feet. A properly loaded pack should fee natural on the back, and you should be able to stand erect without too much pressure on your neck, shoulders, back, or hips. If you're going to be doing a lot of scrambling over rough terrain, consider loading your pack slightly bottom heavy. This lowers your center of gravity and improves your balance, while taking away some of your ability to bear a load.
To make life on the trail easier try to setup a system you can remember and pack your pack the same way each time. By finding a setup that works best for you and sticking with it you will remember where things are quickly in the field. Practice preparing your pack at home. Perfecting your sleeping bag rolling technique and squeezing it into a compression sack should not be done in the pouring rain out on the trail. Likewise load balancing should not be perfected two hours into a hike with sore shoulders and a throbbing hip.
If you're hiking with a group and you have similar equipment consider using identical packing techniques. This will aid in finding something faster in someone else's pack. You haven't lived until you've ripped through your buddies pack looking for the one critical item that seems to always be in the "other" pocket. This can be critical in the event of an emergency.
If you store your gear in compression sacks consider color-coding them. Compression sacks and stuff sacks come in a wide variety of colors, and some dry bags are even clear so you can see what is in them. If you have a color coding scheme you can easily get to what your looking for - all you have to remember was what was in that small green one.
Make sure that some essential equipment like a knife and waterproof matches are kept in at least two locations, one on your person. In the unlikely event a small pocket sized survival kit and a power bar can make you a lot more comfortable.
Also make sure you have three sources of light. We typically recommend a flashlight, a small backpacking lantern if you want to carry the weight and extra fuel, some chemical light sticks, and survival candles as a final alternative. Make sure you have spare batteries, light bulbs and a repair kit for your lantern.
Take some time out and create a logical system that works best for you. By doing this you will save time, effort, and frustration, when out on the trail.