How can I tell if a company is really a suitable/good place to work in?

1) Talk to the people there, preferably outside interviews. Do go for any networking sessions if there are.

2) Talk to any of your friends who have worked there/know people who work there

3) See how much they are interested in developing you

One way to check is to use glassdoor to check for reviews by existing and ex-employees.

Another way is to check with people who you know that might be working there.

Check their online presence although there is no guarenteed way to know until you are there.

Just have to use your hunch and guts to go or not go for it.
I write cool stuff about personal finance and money-saving hacks here.

Check out the company surroundings when u go for interview

Before your interview, check out Linkedin and Glassdoor to see if there are any reviews on working there. See if you have any friends or contacts who can give you some insight as well.

On your interview day, check out the office environment as you are walking in, if you are able to. See if the interviewer schedules an odd hour interview and if many people are still around beyond office hours, this may be an indicator of high overtime.

During the interview, try to pick up any key questions or signs from the interviewer that may indicate something to you about the company.