[TYPO3] migrating custom extensions from 3.7.0 setup to 4.1.1 - how?

[Tomasz Chmielewski]

As I'm making a totally new layout for a website, I thought it would be 
a good time to migrate it from TYPO3 3.7.0 to 4.1.1.

Most easy parts are done, but I'm not sure how I can migrate some custom 
extensions from 3.7.0 to 4.1.1. Obviously, copying the data from 
typo3conf/ext/* is not enough, and some other changes are needed.

Does anyone have any hints on what else should I look at (perhaps some 
database stuff, but I have no clue).


-- 
Tomasz Chmielewski
http://wpkg.org