I'm a bit new at digital art, so I'm still learning some of the basics. Do you have a program to use? I've been using Sketchbook, which is free (on my tablet), but you can purchase a one time upgrade for a fairly low price.
I focus mainly on chickens in most of my art (and am terrible at cats), but a little neat trick I've been doing is tracing what I want to draw, then taking the time to fill in all the details by referring back to a reference (or two).
So for this picture, I did a quick trace to get the chicken the size I wanted in the space I had, and also to get a general idea of the shapes:
It was very sloppy (which I intended because I would rather not trace the details). You can see the image I traced on the right, which is in a separate layer. (You can lock a layer by double clicking it and clicking the padlock in the menu, which I highly recommend doing for layers you don't want to draw on.)
After the trace, I sketched in my outline, then hid the traced layer:
Then I added more fine details, darkened the lines I already had, then started to color:
I like to do a lot of layers, which you can see on the side. That way, if I mess up somewhere, I don't have to worry about erasing too much. On this piece, because I wasn't using a reference on the feet, I had to adjust them a few times to get them right. (If you notice, they're bigger than the picture before.)
Then finally, using multiple layers for the colors, I color, add my background, and finish:
For the coloring, I add the color layers under the layer of just lines. This is so none of the lines get covered over, and I can be a little sloppy if I need to. Then on the background, I use the very bottom layer so again, I don't have to worry about covering anything.
For my digital art, I use a tablet with a S pen. The S pen is like using a regular pen, though it only works on my S Series Samsung tablet. Some people can do digital on computers using the mouse, and others use their finger on their touchscreen devices. Personally, I can only do it with a S pen on my tablet. A stylus pen could also work as it's basically the same thing.
Hopefully something I said here helps. Again, I'm still new to digital, and am still learning the basics. Happy drawing!