The first thing is to focus and make a list of all the things you can do in order to get some extra cash. You also need to take out the time you would need to perform a task in order to get the extra cash. Once you figure out what you can and cannot do, it is time to go hunting for the appropriate part-time job.
If you are good with kids, then becoming a babysitter should be at the top of your list. This job requires little hard work and if you are lucky to find a decent family then all you will have to do is feed and put the kid(s) to bed while you can enjoy watching television for the rest of the night.
If babysitting is not your thing then you can always become a bouncer (provided you have a strong built). Being a bouncer means you will have to work during the night which would allow you to continue your day job. This work requires you to maintain order in a bar or night club and if necessary throw the troublemakers out of the place.
If you love cars and know something about engines you can always work in car repair garage which will help you make some extra money and enjoy being around cars.
You can open your own business on a small scale which you can look after when finished with the day job. However, maintaining balance between the two activities can be tricky.
If you have a particular talent you can become a street performer and exhibit your talent as bystanders appreciate you. Most people can end up with a decent amount of money by the end of their act. This money is often left by the people in a hat or any other item related spread out by the performer.
There is a whole world of secondary employment opportunities online. You can become a blogger, a freelance writer, a graphic designer etc.