Here's my "general" guide to tendonitis based on what I've seen.
1. Rest. Especially if it's overuse.
2. Ice after any use & when sore. 15-30 mins per sessions for couple times a day.
3. Stretch flexors, strengthen extensors *until* pain subsides (medial epicondylitis). Then strengthen everything (my pref = rice bucket)
4. Self massage... cross friction and myofascial release the whole area inbetween both joints that surround it (shoulder to wrist for medial epicondlyitis; ankle-hip for something knee; etc.). As much as possible... at least 30 mins a day if not more. Also, tennis ball/golf ball areas & foam roll
5. Anti-inflammatories/NSAIDs. Fish oil is a good one.
6. Stay away from painful exercises. Period. It hurts, you're done.
7. Light eccentric exercises tend to help
8. + joint/cartilage health supplements like glucosamine & chondroin sulfate, MSM, shark, etc. Might be a good idea to start eating the cartilage and tendons off your meat too.