I'm going to add my thoughts, belated though this is. First, welcome, "Duck"! Nice to have you.
One thing that occurred to me in reading all of the excellent suggestions above, is that not all descriptions are visual. Scents and sounds are commonly described, also; taste and touch less so, I think.
I have a couple of bits of advice, the first being kind of Gestalt-y. Try focusing, really concentrating, on different things. Let's say you're outside and concentrating on sounds; close your eyes (to help you focus better) and listen. You might hear birds and traffic, sure, but. Are there different bird calls? Is the wind rustling the trees? Do you notice the whoosh of tires on the pavement? Details, child, details!
You have to be aware of something before you can describe it.
I strongly agree with the read, read, read advice. This will help you learn what you want to do--and what you do NOT want to do. Mary Stewart is an author who can take you TO whatever spot she's writing about--you can see it in your mind quite well. These descriptions are quite detailed.
But, as has been pointed out, too much detail is not always good! And I for one have not bothered to try and figure out the parameters ahead of time, but I sure know 'em when I see 'em. For example, if I read that someone was standing "one hand on hip, toe tapping impatiently", I don't need a description of the facial expression, and in fact I far prefer to be left to imagine it. But I can only talk about something like that "case by case"; I can't carry it on to a generalization, I don't think.
