1-Find out exactly what speed you are
supposed to have. For example, I have a 6mb download / 1.5 upload connections.
2-Find an internet speed test site. If you're in the US, I recommend
THIS ONE.
3-Test the speed against multiple locations (for example, with the link above there are multiple locations to test your speed against). If it
averages out to the speed you're supposed to get, or if 2 or 3 sites show the speed you're supposed to get then your internet is fine, and it's not your connection. Otherwise you need to make some calls.