Below are some suggestions regarding First Aid Kits:

Look for variety of components
Many first aid kits attempt to sell a kit comprised of a box of adhesive bandages and a few tablets. How many different type of injuries will this kit treat? Not very many! Don't be fooled by quantity of components, look for variety of components! The idea is to include components for real life emergencies, not what might let the kit sell for a few dollars less.

Make sure all basic categories are covered
Any first aid kit should contain at least something from the following groups: Antiseptics (something to kill germs to prevent infection), Injury treatment (items to deal with injuries such as butterlfy closures and cold compresses), Bandages (a variety of bandages to dress and cover a variety of wounds), Instruments (tweezers, barrier gloves), and Medicines (analgesics at a minimum).

Kit organization
First aid kits are only used in a time of need. If you, or someone you are near, are injured and need assistance a first aid kit won't do any good if you can't find what you need. Look for a kit that has its contents nicely organized so you can locate supplies readily. 

Quality components
Adhesive bandages that don't stick, poorly shaped bandages, component packaging that falls apart, a case that doesn't stand up... a poor quality kit is the last thing you need in dealing with an emergency.

Information
A first aid kit does no good if you don't know what to do with it. Frankly, most first aid kits include some kind of guide, but their usefulness can vary widely. Make sure the first aid guide in your kit is from a credible source, contains the latest medical advice, and make sure it its laid out in a way that can be understood when under stress.