Do not burp or yawn during tefilla. If you need to yawn cover your mouth with your hand. (ShA 1)
Do not spit during tefilla. If it is disturbing your kavana, you may absorb it into a cloth or spit it out behind you. (ShA 2 – MB 4)
“Tefilla” is considered until you take your 3 steps back at the end. (MB 3)
If your tallis slips off its place you may adjust it back as long as it did not fall off completely – because atifa would be a hefsek. If it disturbs your kavana being without a tallis, you may put it on when you finish the beracha you are saying. (ShA 4 – MB 13,16)
Make sure your glasses fit tightly before tefilla. (MB 15)