Salsa is one the easiest appetisers to make but getting the taste balance right can be tricky. For the best flavour, let your freshly made salsa marinate for a little while before serving it. If you're planning for a party, instead of serving it fresh, make it the night before and let those flavours mingle.
By giving that fresh salsa time for its ingredients to really get to know each other, you'll get more complex flavours as the ingredients combine. Ideally you can let your salsa sit overnight, but if you're in a hurry, an hour will do. In that time,the salt will also draw the water out of the tomatoes, which results in a soupier texture.
If you like a more liquid salsa, let it marinate for longer than an hour, then serve. If you prefer a chunkier salsa (like pico de gallo), serve it sooner rather than later.