IMPORTANT: Focus on proportion and simplicity, that includes simple 3d Shapes (Spheres, cylinders, Cubes etc.)
Practice these methods and I 100% guarantee you drawing will become much easier and you will get better. Drawing is NOT a talent it is a SKILL. Always remember if you have a hard time drawing or painting something it's because you aren't thinking about it simply enough.
I know the drawing sucks but i was only making this for a dude on conceptart.org so i didn't spend much time on it (under 10 minutes for the drawing but the actual writing to a bit of time). Anyway i decided to upload it here because i think it might help a few more people.
If you have any questions at all feel free to ask!
I haven't updated my DA in a while so if you want to see more up to date stuff check out my conceptart.org Sketchbook here:[link]
and sorry for any spelling errors.
Edit: BTW I didn't include a lot of information like straights against curves, rythm, gesture and more about the tension and those are all a major parts of this whole thing. Idk just google it or something... Srsly, google is one of the best tools ever.
Also this isn't the only way to draw... it's a really good way imo (that's why i shared it) but try others and combine all of the aspects you like into a method that best suits you.