Not all bags are created equal. Here are the 7 Keys to Picking a Golf Bag.
Stand vs. Cart
Do you walk or ride? If you predominantly walk than having legs on the bag will make it much easier when setting you bag down. But if you use a buggy/golf cart then having a Cart Bag might be better as it will sit better and make accessing your clubs much easier. An added benefit is that Cart Bags tend to have more storage.
Top Dividers: 4-6-14 Way
This is the area where you actually put the clubs. Common configurations are 4,6, or 14 way dividers. The 14 way might be great if you want each club to have a specific spot - this might make it easier to spot a missing club. Typically those who walk want the 4-6 way dividers so they can "nest" the clubs and reduce the noise. However if you ride, pick the one that makes it easiest for you to grab the clubs you want quickly.
The number of pockets small and large could be an important aspect in your selection. Lighter weight bags and many stand bags tend to have fewer pockets. There will still be enough space for a balls, and tee's and maybe a rain coat but don't expect much more. Cart Bags tend to have dedicted space for things like range finders, your keys, balls, and large compartments for rain gear. If you tend to store then make sure you get a premium stand bag or a cart bag.
While some bags are have basic water resistant fabric they key to keeping your stuff dry inside are the zippers. The bags that are better for foul weather conditions will have covered/sealed zippers. Look for bags that indicate water proof and then check the zippers! None of them will 100% protect your gear for long though so if that's important then consider getting an external cover that goes over the bag completely.
Most companies offer a between a 6 months -1 year warranty on manufacturer's defects. Be sure to check this out and keep your receipt.
For many golfers this is where they start in picking a bag. It used to be that players picked a bag based on their brand of their kit. In today's game fewer weekend golfers or pros, are sticking to one brand. So pick the bag that best suits your needs!
Most models come in different colour combinations so be sure to check out the options. If you want to customise your bag with a logo or your name, then be sure to look for a removeable panel. Unless you go full custom you will be limited to certain areas. Remember not all bags can be customised.