Never too old - good for you for taking an interest. I agree that taking some casting lessons from a reputable shop is a great place to start. Some of us are "self taught" - I didn't have my first casting lesson with a qualified instructor until 30 years into my flyfishing time - but it was amazing how those lessons straightened out some long-practiced bad habits.
I would also say that the other best thing to do is read, read, and read some more - from the classics (e.g., "Masters on the Nymph" was a seminal one for me, as was Charlie Brooks' "Nymph Fishing for Larger Trout"; Gary Lafontaine's books; etc.) to the wealth of great stuff available today on-line.
I have found that keeping a good fishing diary has also been very helpful as a learning tool (particularly for those of us whose memory may not be quite what it used to be), particularly from year to year - noting not only whether you caught any fish on a particular outing, but other helpful observations such as insect activity, water conditions, weather, etc.