In order to keep boredom at bay, one needs to have a bunch of fitness activities to choose from. But as always, if you are starting something new, that needs better attention.
I started with skipping rope after a long lay off from playing soccer which is quite a balanced game except for the risk of injury being pretty high. Then I moved a bit towards cycling, but I was scared to venture out in Bangalore traffic. When we moved to our new apartment, a brand new swimming pool was very inviting. For couple of years I was a regular swimmer and I learnt swimming techniques that helped me improve my swimming a lot. In between I ran a 5K and 7K, with swimming as the main training event and running once in a while. Then I migrated to yoga mainly because of a computer related injury and got a bit serious about it. I was trying to master "seershasana" when the running bug hit me again. Now I am trying to mix it up so that I don't ignore other type of events with my current interest shifting to long distance running.
What kept my interests on all these(except may be cycling) things were some great books that explains the basics and techniques that sounded very natural. For example, run-walk technique, total immersion technique. I have to thank Jeff Galloway, Terry Laughlin, Iyengar, the yoga guru and Ken Solis for their great books!