I have done this few times and for me doing a side project in the new area always helped. Few other ways: - online courses - books - take notes, but do read up

I have done this few times and for me doing a side project in the new area always helped. Few other ways: - online courses - books - take notes, but do read up about them - see if the new team has a 'new joinee getting started' kind of document Lastly I strongly recommend letting everyone know you are new to the domain. At the min. it will set expectations and usually you will get pointers.