Hi,
1. You could talk to your teacher or you could ask Fred to help you.
2. You could talk to your teacher. Or you could ask Fred to help you.
3. You could talk to your teacher, or you could ask Fred to help you.
4. You could talk to your teacher; or you could ask Fred to help you.
5. You would talk to your teacher or you would ask Fred to help you.
6. You would talk to your teacher. Or you would ask Fred to help you.
7. You would talk to your teacher, or you would ask Fred to help you.
8. You would talk to your teacher; or you would ask Fred to help you.
1, 3, 5 and 7 are OK.
Don't start a sentence with 'Or', as in 2 and 6.
Join with a semi-colon or with a conjunction, but not both, as in 4 and 8.
A comma after 'teacher' is optional, so it's OK.
Both would and could are OK, depending on the context.
Best wishes, Clive