Tips for golfing in TI-BASIC
Your calculator is pretty smart at inferring the end of lines for you, and thus you can omit quite a few characters.

:Disp "HELLO WORLD    //is the same as...
:Disp "HELLO WORLD"


For( loops have a syntax like this - For(variable, start, end, increment), but you can omit the increment and it will use 1:

:For(A,1,5     //is the same as...
:For(A,1,5,1)


and you can omit ending parentheses (at the end of lines) across the board:

:Output(1,1,A
:int(A
:round(A
etc.


Tested on my TI-84 Silver Edition calculator

If you think this is more than one idea (inferring endings) then I'll split them up