Write up your workout plan and exercises on your phone or on paper so you know what you are going to do.
I always have a plan before I go to the gym, otherwise I'll just buzz around in the gym and do 2 sets on one machine then stand there and try tO figure out what my next exercise will be etc
If you don't have time to make a plan before hand. Then step on the treadmill or sit on the bike and think out a plan. Then you can feel more confident.
Don't let your ego get in the way, ask for help if you need it!!
Create a good workout playlist! If you have good music it will motivate you even more and get you pushing that bit harder!!!
Depending on what your goal is between 8-15 reps and anywhere from 3-12 sets. (I can do up to 10 sets on one exercise sometimes.)
The amount of exercises i do depends.... sometimes 4 exercise sometimes 12.