help tuning

Hello I am new to shooting trad but i love shooting my recurve. I am having a hard time tuning my bow. when i cant my bow slightly the arrows shoot fine but when i tried to change my form and shoot with my bow prety much verticle and my body position straight the arrows fly very poor. they wag from side to side and i cant shoot consistant groups. I want to shoot standing straight up because it is easier to use back tension as apposed to leaning in with my bow slightly canted. I have read about guys making sure their rests are set up properly and i dont know if mine is or not, i shoot off the shelf. my arrows bare shaft tune pretty good but i shoot a full lenght arrow so it is hard for me to do any adjusting because i cant cut any to stiffen it up. i got ricks video in the mail and am really excited to check it out. i am a beginer so any tips would be helpful. I think i need help with the real fine tuning stuff.
thanks
dc