Thank you both, you answered many of my questions I had. (I would like to know what the heck I have been doing..)
NickFit saidAs for when is a good time to increase - when you can consistently lift your current weight for your target reps fairly easily. In my opinion, the last rep of each set should be going to failure or close to failure. Once it's no longer to failure, you are not giving the muscle as much encouragement to grow. Therefore, increase the weight.
Currently im working on machines.. I know it's not recommending however it's working for me and i'll stick with it until I am ready to move on...
I usually do 3 reps of 15 per station. However when I increase weight I make sure I do at least 12 reps. My question is: Should I increase the weight when the first rep feels "easy" and the next two push me to failure?
And when increasing weight I have been doing so with 5lb every increase, I assume that is the way to go.