Picking the best MLB games to watch tonight is mostly about timing and matchup, not loyalty. With 15 games most nights during the regular season and a four-round postseason in October, there's usually something worth tuning in for. The Major League Baseball format is summarized in plain language on Wikipedia — best-of-five Division Series, best-of-seven League Championship and World Series — and that structure matters when you scan a daily slate.
A routine that works for me: open the official schedule on https://www.mlb.com/schedule, filter for first pitch in your time zone, and look for starting pitchers with a low ERA over their last three starts. ESPN's daily schedule at https://www.espn.com/mlb/schedule is a decent second opinion when you want to compare broadcast windows.
In October the call usually narrows itself — pitching matchups get tighter, off-days shrink, and every game is elimination. During the regular season the deciding factors are more boring: who's still in the race, who's on a hot streak, and whether the better starter is on the mound.
For a longer-running discussion on this kind of matchup logic and where the fan community lands on it, this thread has been useful: https://intensedebate.com/people/themartinjones