new garden

My daughter is moving into a new house. I want to help her with her garden and although I am good with plants and garden maintenance, I am not very inspirational about design. At present her garden is a blank rectangle measuring about 42 foot by 30 foot bordered by a fence on 3 sides. It is entirely covered in very weedy short grass (more weeds than grass!) with a huge holly tree in the middle. It is crying out for borders next to the fences but it seems a bit boring just to put straight borders round a square lawn so what shape could I have for the lawn? And how do I make the lawn grass instead of weeds?