In addition to the wall and YouTube, do:
- find partners
- important to play actual games
- play against people at your current level or a little better than you
- join your local league/club
- join online tennis sites, leagues, ladders
- learn rules
- watch some match on TV
- search “tennis rules” on YouTube
- practice on the wall
- serve – the most important shot in tennis
- forehand – you will use this shot most of the times
- backend – will be your main weakness if you don’t practice it
- play real matches
- you will not get better just by practicing and watching YouTube