If you want to get more into it; 1gram of protien per lb of bodyweight is the general consensus if you're trying to gain/maintain lean mass. Carbs are you're friend too, mainly complex; brown rice, brown bread, baked potatos, oatmeal etc Polyunsaturated fats are the good kind; from food like fish oils, peanut butter etc and little bit a day is supposed to be good for you too.
If you want to get even more into it, you want to try and eat your bodyweight (in lb's) x 15 per day calorie wise. So a 10st male (140 lbs) would need to eat around 2100 calories a day.
Generally speaking, there are 4cal per gram of Protien, 25% of your daily calorie intake should come from protien, that's 525cal which works out at around 132g. Similarly there is also 4cal per gram of Carb, around 60% of your daily intake should come from carbs, thats 1260cal 315g of carbs. Finally, you get 9cal per gram of fat, 15% of your daily intake here gives you 315cal which is around 35g of fat (the good kind).