There are several ways to take care of your problem.
1) Change all the wiring to copper.
2) Pigtail with copper wire and al/cu wirenuts to all new devices
3) Use copalum at all your boxes (this method is the best, besides replacing all your wiring to copper). Basically it cold welds the aluminum to the copper and makes a molecular bond. It's pretty expensive, and you'll have to look to find someone that actually knows how to do it, and has access to the crimping tool.
Going around and tightening your devices won't hurt, but won't be fixing any longer term issues you may have with the aluminum wire.
Keep in mind that if the original installation was done correctly, your circuits aren't overly tapped, and all the wires are on the appropriately sized breakers, then you may not have to worry much.
Just run dedicated lines to any your new circuits. In other words, don't tap off these circuits.
Hope this helps.