The first time I germinated seeds, I lost several due to overwatering. With some time, I had to create a foolproof tutorial for germination (for myself!), and now I have 100% with good fresh seeds.
I don't use the paper towel method, only special germination substrate. In my area I can get PGX for germination, it contains peat and vermiculite, and works very very well, but It can hold a lot of moisture, so I do as it follows:
-Take 50% of the substrate and slowly add water until it is saturated. At this point, the medium can no longer hold more moisture, and starts to drip.
-Take the other 50% (which is dry), and mix it with the first half (the moist one). Mix it well and you will get the perfect amoint of moisture in your medium. Depending on your medium, you can try 40%-60%.
Next, pick a hole 0.5-1cm deep and put your seed in there. Cover it gently and add 5 drops of water over the covered seed (only 5 drops!). You don't need to add more moisture for the next 3-5 days. If the medium surface starts to dry (and only if it starts to dry), spray a very little amount of water till it gets moist again, back to the original moisture content (50-50, only experience will tell).
Also, it is very important that you prepare your medium only when it is going to be used, otherwise the ph will climb due to activation of limestone (PGX contains limestone).