Start out with a couple of overnight or weekend trips. Keep them short and easy, just to get used to the experience of touring. Test every piece of gear before you go on the longer trips. Make sure you have everything you need to set up the tent. Make sure you can use the camp stove and cookware.
The bike will handle differently when it's loaded for touring and you won't be able to go quite as far or quite as fast as with an empty bike. Get used to this by doing short treks close to home.
When you're trying something bigger, plan for anything that could realistically go wrong because eventually something will go wrong. If you're looking at off-road touring, then you're completely on your own and that's not always pleasant. When you plan your trip, it's a good idea to be a little conservative or pessimistic. You'll probably have a wonderful trip without incident, but sometimes it doesn't work out like that. Contingency plans are good.
Be sure you're ready for multiple flat tires or a broken chain or other similar issues. If you've got to walk your bike 20 kilometres because you've got a flat tire and no way to fix it, that can be a real downer. Likewise, if you're stranded because of a minor mechanical mishap, you won't have a great day.
And while you're at it, make sure you've got the clothing and camping gear you need if a summer storm comes up. Being cold and wet is not fun, especially if you don't know when the rain will end.
Good luck and keep us posted on how it goes when you do your tours.