Consider her comfort when planning dates.
Don't make reservations at a restaurant where you know the chairs are small or take her to an amusement park where she'll have to squeeze into a rollercoaster seat. If she is self-conscious, she won't have fun. Try to take her to places where there will be people of all shapes and sizes; for example, go to the mall or an outdoor festival. Don't plan anything active, such as hiking, unless she suggests it; she may be embarrassed by being out of shape or unable to keep up.
Never mention her weight or size, even if it's to compliment her on it.
Focus on who she is—her personality, interests, hobbies and dreams. Don't ask if she belongs to a gym or plans to join one. If you're together at a restaurant, never refer to her eating habits. Comments like, "Should you really be eating that?"—even if well meaning—will likely bring a sour end to your date. Keep the conversation light and positive and remember to tell her she looks lovely.
Friends & Family
Introduce your special plus-sized girl to your friends and family as soon as you both feel comfortable.
Some girls may begin to feel that you're "hiding" them if you don't introduce them after a reasonable period. During activities with friends and family, keep the conversation general and involve your girl as much as possible so that she feels included. Praise something about her in front of others. Instruct less-than-tactful family members not to mention your girl's size or eating habits.
Out and About
A plus-sized girl may be unusually insecure about her weight and your relationship.
Keep your attention on her throughout your date; don't ogle or flirt with other girls. Make regular physical contact to show your affection; hold her hand, put your arm around her or give her a quick peck on the cheek. Handle embarrassments, like a too-small chair or a rude comment from a stranger, with aplomb and humor. Show her that you're attracted to her no matter what and that she can feel completely comfortable with you.