Introduction to Modeling

The first key with modeling is vision. You have to know what you want to achieve as your endstate. Now I'm not saying you will get there, I usually don't. But without that vision your models, and your army as a whole will not flow together, especially with bases. Your vision will likely change as you work on individual models, you will vary what you wanted to produce based on funds, materials, and time. Make sure that you don't break too far from the overall plan for your force or you will end up with something looking disjointed.

The second key is having materials. Collect all sorts of random things. You never know when that bit from another kit, that rock, that plastic, that cloth will be useful to create something impressive and unique. Try to ensure you can see something you would use it for so you don't turn into a pack rat. You don't need to buy basing kits (it does make it easier) when you can collect most basing materials around the house and garden.

The third key is making mistakes. You cant be afraid to fail when you trying to do something new, something different. It might not work perfectly the first time, but that's OK, just do it again. I have broken many things when trying something new, some were recoverable, some were wrecked. I have a Warhound Titan in pieces that I have to rebuild because I didn't secure a hip joint properly. But I also have a second Warhound that is rock solid because I learn't from my mistakes.

The fourth key is having the right tools. The right tools allow to to file just the right amount off instead of slicing too much with a blade. The right tools let you polish that sculpted part so that its indistinguishable from the plastic and resin around it.

While there is not much anyone can teach you about the first key, and the third key is inevitable, I can give you some ideas about the second and the fourth key.