What I've learned so far based on both work and personal experience.
* Go with LTO. The more recent the better but what you can afford also works. I'm using LTO-4, which can store between 800gb to 1.5 TB with compression enabled.
* Make sure your system is fast enough given the specs of the drive you get. This will make your backups faster and also avoid "shoe shining" where the drive spends a lot of time going back and fourth and wears down the media.
* If you're doing long term archiving, tapes last about 10 to 15 years or more depending upon how they are stored.
* Follow the 321 rule. 3 Copies on 2 different forms of media with 1 copy off site. I'm archiving to two hard drives and one tape. One hard drive will be stored off site (for me, at my parents house).