Efficiency can be increased by making sure you do a few things correctly each and every time. Here's what I would consider important points to increasing you gravity:
1.) a good crush on your grain. Typically you want to crack your grain to the point where your husks are mostly intact but not shredded. You can get better efficiency by crushing the hell out of it but you will certainly run the risk of a stuck sparge. You can add rice hulls to the mash to counter this so really the crack is up to you. I'd say go with a crack where the hulls stay mostly intact, but if you like taking risks, crack the hell out of it and add rice hulls. Don't say you we're not warned though.
2.) a good mash always break down to temperature and time. A good rule of thumb (although it can always be broken) is higher mashes for a lower time and lower mashes for longer times. The key thing about the mash temps are to do a mash out. No matter what, raise the mash temp to 168 -170 (no higher than 170) and hold for about 10 minutes. This stops the mashing process and also makes sure the sugars are all "loose" from the grain and can freely be drained. If you don't have a setup where you can raise your mash temps use one of the online sparge calculators to find out how much boiling water to add to the mash to raise your temp to the desired goal. One tip for you here, if you add boiling water have some cold water on hand to drop the temps if you overshoot that 170 degree mark. You don't want the mash over 170 or you run the risk of releasing tannins and a harshness from the grain.
3.) sparge slow. I don't like to wait when I sparge but it is really important to sparge slowly to get the best extraction out of the grain. Some guys can take an hour to sparge, take as long as you need just don't go fast. Slow moving water will wash the grain more efficiently. Go slow and watch that efficiency rise.
If you can stick to these three items, your gravity will rise. One item I personally always do as well is to balance your ph to around 5.3 (above 5 lower than 5.5). If you can't tell, I've had this issue as well. Do what ever you can to follow these rules and you will have no problems.
Good luck.
