The easiest knot to tie line to line that I have found and use is a knot called the double uni... I am sure a lot of people on here chose or prefer the blood knot , but Ifind it time consuming and a pain to tie , I lose track where I am at.
As for the casting , I agree with the earlier posts , you are not pausing long enough on the back cast before you start your forward cast.. turning your head to watch will help... I found the biggest help to me , was to picture myself throwing the line not whipping it... Try and slow everything down and get comfortable with smooth acceleration forward and backwards.. For me , if you go with the 10 O' clock - 2 O'clock method... After the back cast and pause you should concentrate on your rod smooth acceleration such as from 10 - noon shouldnt be as fast as from noon - 2 and so forth coming back 2 - noon being slower etc...
I hope this helps you out , its just the little tricks I used and it seemed to help me out...
Good Luck out there , I hope to hear feedback from you in the future of all the poor fish that hace fallen victim to your fly
Jer