According to me, she,the girl you wish to marry is somehow a relative to you.
First, you get confirmed whether their gothra and your gothra are not same. If it is same one you cannot marry her as she belongs to your gothra and therefore related equal to your sister.
Second see the age difference between you and her
Third, you get acceptance from your parents as well her parents
If the three above satisfies you need not see any other thing and proceed further.
The marriage between relations, though objected by science, cordial relationship you can expect in such marriage as it minimize the misunderstandings between you and her. The major misunderstanding between couples are due to the follow up in the house practices. If she is somewhat related whether close or distant, she knows the rituals, followups etc., of your family as almost similar to theirs. Many breaks in marriages are only because of mutual understanding. In some families the incoming bride very well understanding the practices of the husband's house and she very firmly attached to the family people of the husband's side. This itself a tonic to the husband.