Consider his personality. Many people, guys and girls alike, have a flirty personality, and that does not necessarily mean your player is playing you. It is most likely that the qualities that made you fall for your player are the same qualities that tend to make you jealous. Remain calm and try not to get mad or jealous until there is a real reason to do so, as his personality will not change simply because he is now in a relationship with you.
Be friendly with her group of friends and pay special attention to how they treat you. If your girlfriend is a player, most likely her girlfriends will treat you like the flavor of the week. That is, they won't make an effort to get to know you and they may treat you like you are a joke. If it becomes obvious that you are being played and you can't deal with being your girlfriend's flavor of the week, get out of the relationship as soon as possible.
Go with the flow, the best way to deal with a player. You may really like your boyfriend and he may really like you, but its better to admit that he is a player than to fight it. Decide to date other men casually. By mutually dating casually, you can both take the time to decide together if you want to take it to the next level, while at the same time eliminating feelings of jealousy and spite.
Call it quits if you begin to feel emotionally taxed in the relationship. No matter how beautiful or wonderful you feel your player girlfriend is, if her attitude and player personality makes you feel bad, it's better to cut your losses before someone gets hurt.