First of all, do not panic. If there were ever one particular rule to follow in plumbing, it would be to remain as calm as possible. Remember, your dealing with a toilet leak, not a plumbing catastrophe. There has to be a reason for this to be happening. Even though toilets are strong fixtures, they do take quite a lot of stress during their lifetimes, and as with anything, that stress can reach a (in this case) literal breaking point.
Aside from not panicking, the first thing you want to do is turn off the water to the toilet in question. By cutting off the water to the toilet, you only have to contend with the water still in the toilet itself. You may not think it, but significant water damage can occur with even a small leak being ignored or not noticed. If you’re having trouble cutting off the water at the toilet, you might have to shut-off the water at the main line to the house. This is certainly the bigger inconvenience, but in either case, you need to know how to perform these tasks prior to the leak.
Next, start inspecting the toilet from every direction and try to identify where the leak is coming from. This isn’t always the easiest thing to do, especially if you don’t have a plumbing background, but it’s not impossible. Do the simplest things first like looking at the connection of the water supply line to the toilet tank. Look around the base of the toilet and see if there is water coming from there. Identifying the location of the leak will give you a better chance of knowing how extensive the leak repair may be.
Finally, if you know where the toilet leak is, and you’ve got the right tools for the job, you have to ask yourself a big question — can I handle this on my own or do I need a professional plumber to come save the day? It may seem weird to think that you’d bypass the chance to be a DIY super hero, but you have to judge the amount of time to make the repair, the number of attempts you’ll need for the repair, and if you run into any issues, you need to know whether you can navigate the snag.