As with any way to make money, the best way of making money online is to follow your passions. First find something you love to do, then find a way to use it for making money online.
There are many websites with ideas for making money online. Some are scams, but many have good ideas. To start making money online, look through sites that offer ideas in the field you are intersted in. Remember that making money online is still a job, and you want a job that you like.
Once you have narrowed down your ideas, consider costs. If you are on a budget, it will narrow down your ideas even more. For any program that you have to buy into, find other people who have worked in the program to see if it really made them any money. Some people make money online by selling programs that don't work that well. Make sure the costs involved in the program you are buying make sense. If they do, and if you find others who have been successful, you might be on the right track.
You also need to consider your time commitment. Find a way to make money online that won't take up all of your spare time if you are already working a full time job.
Once you have determined how you plan to make money online, spend the time you need. Many people start an online business but lose interest and quit. Find a business that you love so you want to stay with it. Finding a way to do what you love is the best way to make money online.