You can glean a lot of information from the various modeling websites and forums. All you have to do is read through them...or if they have a search feature do a search on a particular question/topic you are interested in.
Post your questions too, many modelers here are happy to answer questions and provide guidance. Detailed questions get detailed answers...pictures help a lot too.
DVDs...yeah there are some out there but they can be pricey...Youtube has a slew of modeling videos some good some not so good but the price is right. Occasionally you find a great one too!
Regardless of what you build...armour, aircraft, ships, cars or figures you going to use the same basic techniques. Master the basics and you can build anything! Some older modelers I know and respect are of the belief that if you can build aircraft models you'll have a head start on other subjects, because cleanliness in fit and finish is critial. Aircraft model reveal more than tanks do...hence if you can perfect the plane, the rest are gravy.
I suggest you subscribe to my newsletter (I cover basic through advance techniques), and visit other modeling websites. Each website has its own "personality" and some are geared towards specific subjects such as armour while others are geared towards cars, planes and space.
Lastly, get involved in a local modeling club such as an IPMS chapter. A good club will build your skillsets rapidly and allow you to meet others who share your passion. Much of what I know today came from my friends and fellow modelers. Fortunately we have two excellent chapters (though 100 miles apart) that I attend regularly...both are very active and provide an excellent resource for information and how-to demos.