The basis of any great relationship is the foundation that you build it on. Knowing each other as friends first is a great way to earn trust slowly as you the relationship develops organically.  Having a strong friendship as a core to your relationship will help you tell each other everything and give time and attention to each other easily while looking forward to being with each other. Give your partner the best gift of friendship, the gift of total and complete acceptance. Accept her as she is without expecting anything in return to strengthen your relationship by strengthening your friendship. Your word is your bond, so when you say things or make promises, make sure that you are a man of action. If you are not able to, don't promise or it will cause more hurt than anything.  Promises could be small or large in perspective but realize that making a promise is long term and can affect both you and her future. If you tell your girlfriend you will make it to her birthday celebration, be there. If you offer to help her move her things to a new place, do that. Words and actions that match establish trust. Truth sometimes hurts, but its pain is temporary compared to pain from lies or betrayal. Gain your partner's trust by being 100% truthful 100% of the time. Honesty fosters trust in relationships.  A lie is a lie, big or small. Rethink telling her that you were with your guy friends the other night when you were really with a girl from class as a part of study group. Never answer a question with a lie. Betrayal, even the smallest kind, can derail a relationship and cause your girlfriend to distrust you completely, especially if it touches on a scar from a past relationship that hasn’t yet healed. And it is hard to recover from. Healthy relationships are a result of healthy, honest communication. It’s always better to hear firsthand what happened, and to seek forgiveness then. Being open extends to letting her know pertinent information as well.  Not presenting facts from the start makes you look deceptive and like you were hiding something. Even something small could look ten times worse if you aren’t honest about it from the start.  Keeping your girlfriend in the loop to support you during challenges is equally important in moments of joy as well. Not only will you feel like you matter, but she’ll feel like she matters too because you share those special moments, like getting a promotion or receiving an acceptance letter from a school you’ve been dying to get into, with you too. Dealing with someone with trust issues means dealing with suspicion if you leave out certain details. Grabbing an innocent cup of coffee with a female friend can raise suspicions for a girlfriend having trouble with trust if you gloss over details and she has to hear it from someone else.   Just be forthcoming and, on the day of, state: “I’m grabbing coffee with Sasha today. Cool?” It is a simple way to be honest while showing her that her opinion matters at the same time. If you aren’t hiding, she doesn’t need to be unnecessarily concerned so keep her up to date on what you’re doing with the opposite sex, even if you are just friends.

Summary:
Prioritize friendship over all else. Follow through and be a man of your word. Always tell the truth. Communicate with her to let her know about your ups and downs. Involve your girlfriend in your day to day.