Performance Tweaks/Tools for MacOS (Macbook Pro)

I am using a Mid2010 Macbook Pro (2.5 GHz i5, 8GB RAM, regular HD (no SSD) and still on MacOS 10.9).

I am fully aware of the fact that, as the computer gets older, it may get a little slower due to more space used on the HD, more applications installed etc. etc. However, I feel that in the last few months I feel like the performance has degraded more than it should be. What do I mean by that? Well, it takes longer and longer for me to boot the Mac, applications take longer to start and it happens more and more often that they simple freeze for a short moment. Lately, I even had to use a cold reboot by pressing the on/off button long because the whole system froze when I was simply watching some videos.

Now, I am looking in how to get a little bit of the performance back, i.e., either some tips that I can directly use in the OS or some tools which help me. Unforunately, googleing them brought up a whole bunch of differerent tools, not all of them looking extremely reliable. I'd be grateful if some of you have a couple of tips for me.

Thanks