• what chapter you want to file now
• what chapter you filed before
• whether you received a discharge in the earlier case

You can only get a Chapter 7 discharge if a previous Chapter 7 case was filed more than 6 years ago.  

If you got a Chapter 13 discharge within 6 years, the Chapter 13 plan has to meet certain repayment requirements to permit a Chapter 7 case within 6 years.

If your previous case was dismissed before discharge, it does not count in these considerations.

You can file a Chapter 13 case after a Chapter 7 without any statutory time restrictions.  Some courts, however, question the debtor's good faith, a necessary element to confirm a Chapter 13 plan, if they have recently filed Chapter 7 and received a discharge.

You can freely convert a pending case from one chapter to another.  It is the same case, even though the chapter is different, so these time considerations don't apply.  Generally, you can only convert a Chapter 7 to Chapter 13 before the discharge is entered.