Biggest things you can do is get a high quality screen protector and a decent case that is both hard plastic/metal and has a rubber component sleeve to it.
There are some cases out there you can spend $200+ on that will protect your phone from hammer blows and completely ridiculous level of similar damage.
There are other cases like the outter box defender that are easy to find and work pretty well. Personally I use an outter box commuter, it offers good protection without an insane amount of bulk. I slammed the rear hatch of my jeep on my phone twice and the case saved it (thankfully!!!), with only a small dent in the plastic from each blow. I used to use a incase pop! That offered similar protection.
In the end it's personal choice. Start looking at how much bulk and protection you can stand/need. If you work construction or in similar environments get a bulkier, more protective case. If you are just looking for everyday drops and similar perils get something with less bulk and less protection.
Good guideline is to go with a hard plastic shell and a rubber sleeve other then that read reviews and get what style, color, and bulk you like.