I was searching for ways to record video of all my League of Legends games. Going through different forums and everything until I found a really useful tool. I've used it a few times, and if you're computer isn't so high end like mine, you have the ability to capture, record and share every moment in your game for free! This may not affect your performance.
It's really quite easy, you basically should do two things.
1. Download and install the League of Legends replays - This runs in the backgrounds and records/saves everything. Ensure you contain it running in the background when you are in a game LOL. This may record each moment that happens. Whenever you replay it, you have the ability to scroll around and view everything. There is a slow-motion button, in addition to fast forward and pause. The only thing missing is just a rewind button. Google LOLReplay and click the initial link for a download.
2. Download and install a free version of Fraps - This only lets you record 30 seconds at the same time, so you will have to put them together in a video editor program. I personally use Windows Movie Maker. Whenever you run the replay, Fraps moments that you think are good and deserve the spotlight. You can even keep clicking the record button if you want to record the entire game. It will likely then save all the files in your Fraps/Movies folder. Open them in the Windows Movie Maker and edit it how you prefer. Google fraps download for the download.
That is only needed if you want to talk about with other people via YouTube, or some other video sharing sites. In the event that you only need to view the replays for personal gain, then this is not needed. I've tested this method and it works very well if you are a free method. You can even use other recording software such as HyperCam, but I have had better success with Fraps. In the event that you don't have Windows Movie Maker, or would prefer an alternate, Ulead, Honestech and Power Director are similar and won't break the bank. This software does cost a tiny amount. If you need to adhere to a Free method, I strongly suggest using Windows Movie Maker,
Although might also want to test into VirtualDub, it is just a free editor that lets you cut, reverse, flip, resize, and apply other special effects to .avi files. It's ideal for clearing up videos before entering them to the timeline.