Well I'll be damned! Welcome.
1.) Some general tips, I would say make sure to plan and outline your story well before you start writing. Actually, that part can be sort of interchangeable, oddly I find it helps to write the first page or so in a word document to get a good feel than plot it all out. It's alright if you change up the first couple pages later or disregard it in favor of something more fitting.
Once you have the plot thought out, definitely take some time to think about your characters and how the plot influences them/how they influence the plot and other characters. I generally find I like having a portion of my story notes set aside to write a small (or sometimes long blurb) of the characters story arc, personality, relationships to other characters as a general guide to keep them consistent.
Now that I've told you to obsessively plan your story, don't be like me and make the mistake of taking too much time planning things. Sometimes you just have to make a basic plan and get to it. You'd be surprised at the things that can organically work out when you working through your plot and writing the story.
2. Sometimes you can't rely on motivation alone. I've found that sometimes you just gotta roll up your sleeves and get through the horrid middle parts of the story. What I find works is to have a scene, character, or event in mind that you like so you can get motivated to write until you reach that point. What's nice about this is if you place something fun and exciting towards the middle, it can help you flow right on to the next thing you want to get to. Then before you know if you're almost done!
(These things can often be easier done than said but don't beat yourself up if you need to get away from your story for a couple days)
3. I would say anything by EndMaster. His stories are the perfect example of how to execute large scale branching without completely changing the story randomly due to one choice. What I mean by this is that in his stories the choices you make tend to influence the world around you. For example see: http://chooseyourstory.com/story/necromancer
Whereas some stories like to completely change something due to a choice (which can be well done but generally not good). For example if you have a character eat toast then aliens attack, but in the next read through they find if you eat jello instead the story just becomes something entirely different.
What a lot of people tend to appreciate better is how, exactly, does eating toast or jello influence your interactions with the aliens? Are they allergic to jello? Afraid of toast?
However, smaller choices that don't effect the overall story as much can be well done. It can add some extra lore and worldbuilding options as well as character development that you can see more and different options with each read through. For example see Steve's: http://chooseyourstory.com/story/fear-the-psyker
4. I'll admit, I haven't kept up in my book reading in past years. The reading corner in the forums section would be a great place to look.