How do you improve at tactics?

Hi. I'm around 1750 USCF rated and I feel like I should be better at tactics. I do tactics online at chesstempo.com / emrald chess and my rating over there is around 1630. My rating has stayed 1630 for about a year and a half. I improved from 1400 to 1600 and since then, it has just stayed the same. 

Am I doing something wrong? I feel like I'm just wasting my time because I'm not improving. How do I improve at tactics? Should I read tactic books instead of doing online tactics? Thanks for any replies. 

Do you spend more time doing them now than you did say a year ago?

Also, are there certain ones you tend to get wrong, and others you're strong at?  If it is something like that, then you have a topic you can work on.  Like I know for me ones that are about just material gain I tend to blow as I'm looking for mate.

There are plenty of tactic puzzle books you can carry around so you can tend to the task away from the computer-- thus increasing the time you spend on it.

Last suggestion: in addition to books on tactics (not just puzzle books, but ones with "text" explaining ideas), perhaps working on other areas of chess will help with the tactics in that you'll see tactics but in a broader context: endings, middle games, etc. 

I'm exactly in the same situation. I study tactics at chesstempo, and I've been around the same level in blitz training for more than a year. I believe that's because I really don't have any talent for calculating quickly, and that in reality my tactical abilities do improve with time, although very slowly.

My humble recommendation would be not to cease your training ct, but also add studying tactical master games to your training, preferrably of a player you like. Trying to figure out what to do in tactical situations in a real game and checking your calculations with the actual GM moves, annotations or engine analysis can't hurt your tactical abilities.

Thank you Estragon, Philidor_position and musicalhair! I will follow your advice! :)