I have been reading that you get either a 3/10 year ban if you overstay a visa. How do you know which one you will get? Is there a certain amount of time that you have to overstay to get a 10 year ban that is longer than that for a 3 year ban?

The difference is the amount of time you overstay. I think you get the 10 year bar if you overstay more than 180 days. My husband was deported to Senegal 2 weeks ago with the 10 year bar. He had a deportation order in 1999 that he didn't know about. I am filing a waiver to bring him back. Wish us luck. I have been told that it is a lot harder to get back once you leave, so if you are in that situation get an attorney and stay away from USCIS.

From USCIS website

Generally, the three-year bar applies to those who were unlawfully present in the United States for more than 180 days, and the 10-year bar applies to those who were unlawfully present in the United States for one year or more.

ALIENS UNLAWFULLY PRESENT.-

(i) In general.-Any alien (other than an alien lawfully admitted for permanent residence) who-

(I) was unlawfully present in the United States for a period of more than 180 days but less than 1 year, voluntarily departed the United States (whether or not pursuant to section 244(e)) prior to the commencement of proceedings under section 235((1) or section 240, and again seeks admission within 3 years of the date of such alien's departure or removal, or

(II) has been unlawfully present in the United States for one year or more, and who again seeks admission within 10 years of the date of such alien's departure or removal from the United States,is inadmissible.

(ii) Construction of unlawful presence.-For purposes of this paragraph, an alien is deemed to be unlawfully present in the United States if the alien is present in the United States after the expiration of the period of stay authorized by the Attorney General or is present in the United States without being admitted or paroled.