http://www.livefromplanetdeath.net/wii-sports-cheats-tennis-2/
How do I score points in Wii Sports Tennis in 2 player mode?
My GF and I play on the same team, and we win, but every time we get +-0. When we play against each other points show as just —-, so the +-0 means that there are points on the line, we’re just not getting any. To make things more confusing, we used to get points when we played on the same team, just not anymore. Thankfully, we can get points when we play by ourselves, it’s just that she is a total addict and I never get a chance to play without her and I want to get to pro! It sucks, because she’s pro because she plays while I’m at work, but I’m WAY better than her! (she tells me that I cheat…)
Since you are on the same team only one Mii can get the points. If you are playing by yourself you can get the points because there is only one Mii that can get the points (unless you are versing each other).
You cannot both get the points if you are on the same team. One Mii can get points but the other player needs to use a default Mii or the same Mii as you (if that’s possible).
Wii Sports Tennis Cheats (Blue Court)

