Hey, we've all killed our share of plants! The trick is to learn something from every one that you kill, and then try not to do that same thing again! I've been gardening seriously for a few years now and for the most part know what I'm doing and I still kill a decent number. The only difference now is I usually know what I did wrong! LOL I think the trick is to come to terms with the fact that some are not going to make it--there'll be some plants that you really want to grow but either your climate is just not right for them, or the conditions in your yard aren't right, or something along those lines. And I can speak from experience that when you have a lot of containers in a small space, it's really easy for one to get missed when you're watering and end up dead, or one ends up getting more water than the others and dies from that. Some people have a really hard time accepting plant death, but try not to take it personally or think you've failed as a gardener if a plant dies here and there, I guarantee you even the best gardeners in the world still kill plants from time to time!
Whoever told you to just touch the surface of the soil was wrong as you suspected...the top of the soil will dry out fairly quickly, but just underneath the surface can still be very wet, so if you give the plant more water at that point you'll end up killing it. The best thing to do is stick your finger down in the soil a couple inches and see how it feels down where the plant's roots are. If it's drying out down there too, then give it some water but if it still feels nice and damp then let it go. With containers, you can also pick them up and see how heavy they are and after a few times of finger poking to feel for wetness you'll be able to tell by the weight of the container whether it needs water too. And yes, it does depend on what type of plant you have...you can use the Plant Files here to look up your plants and see what their watering requirements are (if you haven't found PF yet, go to the "Guides & Information" tab and you'll find a link to it). You should still use the finger trick to judge, but for plants that like to be consistently moist, you'll want to water while that area a few inches down is still damp, but for plants that you're supposed to let dry out between waterings you'll want to wait until that area is feeling pretty dry. Sometimes Plant Files will be missing watering info but you can sometimes find it on plant tags or else you can always post here and ask.
