You'll likely pick up a lot just by listening to how your technique translates into what you hear.
On the organ, once you move your fingers from the keys the notes stop sounding instantly - with no sustain pedal to cover your poor legato technique either! So the biggest difference you'll find is that you'll probably end up doing a lot more finger-substituions to keep the note sounding whilst adjusting your hands to move to the next passage.
The flip side of this is that the note sounds for as long as you hold down the note - and won't die away as it would on a piano - so any fingers that rest on the key for a little too long will be equally conspicuous!
Your wrists should also be raised higher than they would normally be on a piano but at the very least they certainly shouldn't sag down.
If you are playing a mechanical ('tracker') organ - where the keys physically move the valves to let air flow through the pipe - you will find that as you add more stops, the action will become very very heavy.
In other words, pressing the keys down will be a lot harder to do than on the piano and you may find finger strength to be an issue at first.
On the other hand, you may have an electrical action where the keys stay uniformly weighted and will actually be easier to depress than a piano's.
Whilst no one listening will notice, you should also get out of the habit of using any 'percussive' style of attacking the keys - the organ doesn't care how hard or soft you press them, so concentrate on keeping things fluid and uniform. That's not to say you play staccato and legato in exactly the same manner, but there should be very little need to be lifting your hands completely off the keyboard; try and do as much as possible through your fingers.
As far as pedalling goes, this will be entirely new to you and so you shouldn't have learned any 'bad habits' as yet. This is a topic in itself and probably best left until you are comfortable using your hands.
However, a few tips:
When using the 'toe' of your foot (the other option being the 'heel'), try to use the ball of your foot rather than the toes alone. You'll probably do this naturally, but this will feel more stable and also make swivelling your heel a lot easier.
When you get on to more 'involved' pedal parts, you'll also notice that you have to physically balance yourself to prevent the pushing of your legs from moving your upper body. When playing the pedal by itself you'll often find yourself grabbing hold of the organ bench to steady yourself and offset the force of pushing down especially on the outer ranges of the pedals. When playing with manual and pedal, you'll be using your hands on the keys to steady yourself - sounds awkward but will happen naturally.
Whatever your preference, you can't play in trainers. The majority of organists will advise you to get a good pair of purpose-made organ shoes. These are similar to ballet shoes, disguised as formal suit shoes - thin but with solid heels and toes.
Personally I never wear shoes, ever - just socks. To me, playing the pedals wearing shoes is like playing the manuals with gloves on. But I know I'm in a minority and whilst some others will say it's okay for practice, they'll always wear shoes to perform.
It's up to you - see what feels most natural.