As with all single player games, the declarer must play against three opponents. Moreover, as a solo player, he must play without any part of the Talon. The full Talon will go to the opponents after game end.
For a Three solo game, you should have at least 8 very good tarocks and the Excuse (XII) or the Moon (XXI) should be in your hand. Additionally, one of the following points should be true:
You should not announce a Better Piece unless you have at least 2 higher tarocks more than needed when playing a Better Caller.