You get accredited by having money.
It's not like one receives a diploma. You have to meet 1 criteria on a list. For example if you made 200 k in back to back years..You are considered an accredited investor. It is up to the company that you are dealing with to do their own DD on who they can do business with. There are a few more things that could make you qualify.
If you are looking to do a PP. If you are not American and dealing with a Canadian company .you may be able to slide in under the "existing shareholder exemption"
There are ways around not being accredited and still participating in PP's