Shorts are ok, but they're amateur hour and there's no money in it in the long run (actually... half true... but there's more potential in features... though I've yet to realize that myself... one day though.)
If you want to make a feature it's all about planning. You gotta have a good script first, and also it has to be longer than you think it ought to be, so when you're finished the first draft of the script it's time of what you figure a feature ought to be, it's time to double it... you can always cut out stuff before you animate it, and it's easier than trying to shoe-horn in more footage after you've done a bunch of shots.
Make storyboards next, stick figures are fine if you suck at drawing or if you don't want to draw the same thing twice during storyboards
Record all your voice actors next, then sync up the best takes with the storyboards and a rough in of the music if you have it, to set the timing for the film. Action shots are a bitch for this part, so I go by 1 second per 'frame' of storyboard as a rough guide, but this always changes.. You should have a rough animatic of your film that's as watchable as the final film at this point. Show this to a friend or two, if they get bored and start talking hockey, then it's time to rethink your script.
Now you haven't created any characters, sets or models for your film yet. This is a good time to look through all the concept art, sketches, reference material, and storyboards to get a feel of the visual style of your film and the world within. Storyboards are a good place to set down concepts, but don't get too bogged down with details, that's for the next step.
Now you go through your storyboards and script and make a list of all the characters, sets, models, props, effects, which you are going to have to build or find. Online sites like blenderartists.org are great places to get models, however these might not be exactly suited to what you need, and once you are proficient enough at modeling it will be easier to build what you need from scratch, especially if you need to fit into a certain visual style (ie toon rendering vs photorealistic etc..)
Once you have everything ready, animate all the "easy" shots: dialog and environment / setup shots. This gets you used to animating again and you iron out your animation / rendeing / compositing workflow before you get to the action shots.
M Dot Strange likes to animate a whole bunch of shots before he does any compositing, I never render more than 10 or so shots 'ahead' of myself, you never know when something is going to be screwed up and it's easier for me to go fix things while the shot is still fresh in my mind.
*presto* easy... you have a finished feature length digima to get rejected from all the major festicals... Archon (70 mins) took 3+ years what with doing scene additions and recomps and totally redoing the voiceovers and audio mix *twice* . Origin I did the right way (as described) in exactly 2 years for an 80 minnute film. A short 10 minute film should take 3 months tops, but it's just about as much work in the modeling and set building stage as a feature: you can use the same models and sets over again for a feature, get more mileage out of them. I've got one model "Dr Monacle's Console" from rocketmen 2 that's also been in Rocketmen 3, 4 and Origin..