Based on my own personal experience:
-how he treats his mother is usually how he will treat you
-kung walang respect sa parents and siblings, he won't have respect for you too.
kaya you have to spend lots of time din with him around his family, so you can see how he is with them (Esp. sa sister and mother niya, mga babae sa pamilya)..lalabas at lalabas tunay na ugali niyan when he is around his family. and lalabas din kung mama's boy ba siya or overly dependent sa family niya. you can see also if that's the kind of inlaws you want to be dealing with (lol)
-take as much time as you need to access kung para sa iyo ba siya o hindi. don't get pressured by him or anyone to make a commitment, especially on MARRIAGE AND HAVING A BABY, just so lang maging masaya siya, pero deep inside alam mo hindi ka pa handa at may doubts ka pa, which follows the next one below....
- don't make life changing decisions based on emotions (taken from Aquacharly), and this goes for him too! making decisions na hindi pinag-iisipan maige, magbibitaw ng promises na hindi naman pala kaya panindigan, etc.
- cliche as it may be, but really: when in doubt, DON'T!
- take into consideration the advises and opinions of your parents about your bf/fiance. They can see outside the box. Makikita mo rin in time kung biased lang rin ba opinions nila (Coz baka ayaw lang talaga nila sa bf mo coz they prefer someone else

) or kung tutuo talaga nakikita nila about him.
- always keep your eyes open for signs/red flags. don't blind yourself. Be guarded at times
- follow the golden rule.
- don't let your world circulate around him only. and don't agree if he demands this from you!
- Make God the center of your relationship
hay ang dami dami pa.

basta mga sis, be careful. Don't put yourself in a situation na wala na kayong self-worth or respect..wag maging overly martyr. magkaroon kayo ng hangganan.