Check out
http://www.lavanet.no/progress/" onclick="window.open(this.href);return false; for a start.
You can choose which expansion you are looking at up at the top of the page. Then look at the guilds who are making or have made progress in that area. Then go to guild page links and check first to see if they have updated their page recently. If not they may be struggling. Look at their roster, their forums, and their recruitment information.
Try and approximate to a first order what the population on servers is, because many servers are having issues.
Maelin, Xegony, and AB look like a good bet (maybe - don't take my word for that).
Then talk to the recruiters or PM or email them. I prefer to talk to real live players using ;tell servername.playername so I can get a good handle on what's up. Then you might visit their /general channel or even take a look-see in the Bazaars to see how many traders there are and how outrageous their prices are for a handle on server population (average traders these days is ~ 100 traders in Bazaar at peak so you might want to use that as a starting point). Bazaar prices on stuff like Spongy Loam, Vanadium (anything) are another indication of server health in general and the dearth or abundance of stuff, and the server personality. For example, if you see Spongy Loam being sold for 30k each (that is very high - average 8 to 10k) with a lot on one trader, there is implicit information there, in context with the other information you can get.
Raiding guilds these days are of 3 varieties. In one they like to raid 6+ days a week and have very stringent attendance policies. Another has 5 to 7 with attendance polices with less rigor. And then the 3rd variety that seemed to spring up from Descendents idea on MM (Saryrn now) is a 3 day a week raiding guild that does raid content but does it without the brute force. There are a lot of those types of guilds on Xegony.
Anyway, that's a start.