Do not use invisible text. This is an adaptation of keyword stuffing. While this can make for a better experience for visitors, the search websites see it as cheating and will penalize you for it if you get caught. Avoid doorway pages. Again, you’ll see a short lived increase in your rankings, but might be dropped from the lists completely when the search sites find out .

Read and follow terms of service (TOS). Nearly any site you use to help boost your rankings will have a TOS. After you start to look for loopholes or justifications, you are moving into black hat SEO territory. Therefore if that happens, take that as a sign to do the decent thing. Doing the above things will go a long way towards avoiding black hat SEO methods. You also will not have to fret about dropping in the rankings if you are caught doing some things wrong.