I have a bit complicated way and it's always a horrible pain in the ass.
1. Happy ending - I check the ending.
2. No love triangles - watched almost all of series without them, some were great, some sucked but it's extremely hard finding anything fitting this criteria, which I haven't seen yet. Most Asian dramas have to incorporate those stupid, pathological love triangles... So usually I fail in this one.
3. I love when there're martial arts, good fighting, lots of action - here again - I've seen almost all typical action dramas from China, Korea or Japan, I can't stand most Thai ones because they're mostly remakes of what I've already seen - so here I fail as well.
After failing point 2 and 3 (1st is a must), I start searching for next, less strict criterias where I succeed with a ratio of around 20%.
4. No stupid misunderstandings, no break ups, no betrayal, no stupid main characters behaving like pussies/assholes/bitches/idiots - as you guess, I fail here miserably too because I've seen most of what's possible, mature and realistic but let's say I still succeed with a ratio of 1/5.
5. The third wheel must be directly and openly refused, cut off without any regrets, any insecurities nor any shit like that - here I sometimes succeed with reccommendations - I'd say that this point is at least possible to fulfill.
Then still - after faling most of those and losing patience, I just scroll through the genres or reccommendations, google it if the specific show fits any of my criteria and give it a try. Here I also fail a lot so I need to drop in the middle when I can't stand those stupid trash people (ML, FL etc.) behaving like idiots in a drama I chose because it wasn't supposed to be stupid/childish while it's still is and someone just has much, muuuuuuch lower expectations towards shows than me - but sometimes I get to the end or just skip half of each episode :-P
Also - once in 10 dramas I decide to watch, I come across something, which I like very much and it's always a surprise since I do not expect it, actually, even if a show has some of things I do not like.
