As far as fishing goes, the #1 cause is trying to throw a small plug, spinner bait or buzz bait with a short stiff casting rod. Graphite is fine for flipping and worming, but fiberglass is much better for cranking. The whipping action of the tip allows you to throw farther with less effort. I went to 6'-6" David Fritze fiberglass rod, and it made all the difference in the world. I went from elbow pain on every cast to no pain the entire day by switching rods. Also trying to throw a C Rig with a short stiff rod will cause the same problem. I now use a Pinnacle Millennia 6'-6" Graphite rod with a fast tip ( good MED action ) and a 10" two handle grip. This works 100% better than the pistol or 8" grips. YOU DO NOT NEED A MED-HEAVY OR HEAVY ACTION ROD TO GET A GOOD HOOK SET. All a stiff action rod will do is give you elbow and shoulder problems and make it harder to cast.
Stretching is very important because is gradually lengthens the tendon and reduces stress on the tissue that holds the tendon to the bone/muscle. This is the source of the pain
You should not exercise if it hurts to do so. It took a week for my pain to subside enough to start with the weights. Again it may seem silly because the weight is so light, but it does work. You are not truly cured until the pain goes away. Usually 4 - 6 weeks. I have also started using the tennis elbow brace. Basically a strap on the for arm near the elbow. When a muscle contracts, it shortens. This pulls on the tendon. The strap forces the muscle to flatten out instead of shorting. This relieves stress on the tendon. I will make the muscle sore, but does not have a lasting problem. After a few uses, the muscle will not get sore.
I also use Aspercream on the elbow each night. Any sports cream should work, but the Aspercream does not smell bad. I put it on liberally and pull a tube sock I cut the end out of over the elbow. The sock adds heat and helps the skin absorb the cream. Wrapping the arm in plastic wrap before applying the sock will enhance the penetration of the cream further. It makes it itch like crazy though. DO NOT WRAP THE ELBOW UP TIGHT like you would for a sprang. This reduces blood flow to the damaged area and can actually inhibit healing. Tendons and surrounding tissues get very little blood flow to them. That is why it takes so long for them to heal. The sports creams can sometimes increase blood flow locally and that is why the soreness goes away faster.
You should also put ICE on the elbow for 15 min. three times a day. This reduces the swelling caused by the irritated tissues. Also do not do it for more than 15 min. or three times a day because of the blood flow issue. The ice is a good place to start for the first week. I use the rubermaid blue Ice packs. I put them in the fringe instead of the freezer. They are soft and it feels great on the elbow. I also use them when I get back from fishing / tennis.
Ice pack is also good when wife smacks you in the back of the head for fishing too much and not doing any house work because your arm hurts from fishing too much. She just does not seem to understand........
I hope this helps some.....Good luck......Jeff