It's TV premier season, and this year has a lot of reasonably ambitious pilots, some of which show some potential for being great, but are going to take some establishing before they get good... if they get good: Gotham, The Flash, Constantine, Forever, Scorpion etc...
So, what happens if you see the pilot, and really WANT to like the show, but the pilot is only "Meh"?
...or worse, it's really close to like... halfway great, but there are a few things which subtract from it to make it either "meh" (Agents of Shield anyone?), or a couple specific things which really turn you off?
Let me just say... give it time...
Don't dismiss something which has the potential to be great, just because they didn't get it right at first.
There are a lot of shows that are now considered all time greats, where the first half season wasn't great, but they found their feet in the second half.
Actually, in some cases like "Cheers", ST:TNG, or "Buffy the Vampire Slayer" even the whole first season was not great, but the networks or production companies trusted the shows enough to renew.
Unfortunately, that almost never happens anymore, because networks don't stay long behind a low rated show... Hell, they'll pull a moderately rated show after 3 episodes if they were expecting higher and have a decent replacement prepped. Sometimes though they'll give a full season pickup pre-air, and the show starts mediocre, but they'll let it run through the whole season to find it's feet.
First thing is to remember, it's just a pilot.
For a pilot, the production values, and shooting scripts... even the characters, and cast in some cases... may be significantly different from the initial pickup shows. You can't really tell from the pilot what the final product is going to look like. If you like the concept and the characters, you've got to give it at least 3 episodes.
If after 3 episodes, you're still in the "Man, I want to like this show, but they're just not quite there" zone, you have to remember those 3 episodes were all written and produced before airing. In fact, the first 6, 8, or even 10 or 12 episodes will have been produced before the pilot is ever aired (though not usually 12... 6 would be common). This means they haven't really seen what the show is doing in front of a real audience yet, and they haven't had a chance to make adjustments.
Sometimes, particularly if it's a production values problem, the show will get better over time because the initial production order was on a lower budget, and the next 3 or 6 will be better.
This is particularly true of higher budget long lead time shows, with a lot of postproduction work... I.E. science fiction, fantasy, and adventure shows like the ones I mention above. They have a much longer lead time, with more episodes in the pipeline simultaneously, so it takes them longer to adjust to the audience reactions.
Also remember, this is the age of six channel multi-terabyte DVRs, streaming services, and bittorrent.
If after 3 episodes you till like the concept and the characters, but not enough to watch every week, or there's still a couple things that turn you off, wait a while, then come back.
If the show doesn't get a full season pickup, then you don't need to bother.
If it gets picked up, let the previously filmed episodes burn off, then watch the first episode filmed after the pickup. If they have the details fixed by then, you can go back and fill in.
... and of course, there's always bingewatching in the winter hiatus, or after it shows up on netflix.