I think it is not so difficult if you are really honest. Many people search for a partner who is very sexy, good looking and maybe rich. These things are superficial and unimportant. You need a person who makes you feel loved and respected, who will be there for you when you are sad or in trouble and support you, and who doesn't love you for those superficial things. When we get old we may not be beautiful or sexy or rich. So the person needs to make you feel safe and happy and make you laugh. Those qualities are the most important ones. If you meet someone you should try to ask yourself if they will support you in bad times as well as good. If not, move on to a new partner.

You ask a difficult question.

These days it is really hard to trust others. Almost 80% of people all around the world just think about their Interests. They make friends to the extent that they can and whenever they achieve their goals they will leave their friends. This way is really cruel. For me, A friend always remains in my life untill she/he does not lie.

You find yourself first.
As Parvin said it's very hard to trust others in this day and age, hard to find someone who looks past all the superficial and materialistic nonsense...Make sure you can trust and love yourself first.
S/he who seems technically or logically right for you may be completely wrong otherwise, and vice versa.
Love is not of the mind...Find your heart and follow it.

What @Ruthi said has worked well for me -- for more than 25/20 years now, with not a single moment of regret (I have two life partners). 

Three guidelines govern our relationships:

Love is a verb.  Take action.

Presume good will in all situations.  When in doubt, presume misunderstanding.

Know each other.  Appreciate each other.  Encourage each other.

Don't sweat the small stuff.  Most everything is small stuff.

Love and attraction stem from the unknown desire to

find somebody with whom to have and raise children.

It is a complex mental process that happens in a short or long time, and it

happens behind the scenes, we don't know the mecahnics about it;

neuroscientists who study this subject know a little better.

In our life we accept many things that just happen in the right way to

our bosy or mind and we ignore HOW they happen.

Falling in love is just one of these, and please note that mother Nature

does not care in this mechanism about our well being, but about the well being

of the next generation, so we should not expect that marriage life to be always

pleasant, we can only hope (and work towards this aim)  that the happy times will

outnumber by far the unavoidable moments of doubt or sufference.