The short answer is to determine your caloric needs, divide by 6, and plan 6 meals that meet that number.
Example I am 200 pounds and want to gain...I use 17 as my generalization for calories per pound for bulking (look in those links below for why) so I come up with 3400 calories a day.
Divide by 6 meals is about 570 calories a meal.
I can use fitday.com as a free meal planner and plan one meal at a time.
I try meal 1:
1/4 cup organic harvest trail mix 120 calories
1 ounce whey protein 110 calories
3 cups puffed rice 165 calories
1 cup whole milk 149 calories
I come up with 546 calories..just a bit short of my goal.
That has 16 g fat 64g carbs and 37 g protein
At 200 pounds and bulking I need about 180 grams protein...divided by 6 = 30 pre meal so I have enough of that
I would want about 50% carbs or 1700 calories divided by 4 = 425 grams divided by 6 = about 70 grams per meal. I am close but could add blueberries and bump it up 6 grams or 24 calories making my meal total 570 calories.
Plan 6 meals today and every day or every week plan one more new meal...in no time you will have a whole menu book to choose from!
As you gain mass...every 10 pounds of muscle requires another 350 - 500 calories to support it! So you have to bump up the meal contents as you grow!
Its more in detail in here:
For Gaining Mass http://www.discussbodybuilding.com/For_Gaining_Mass/m_111173/tm.htm For Losing Fat http://www.discussbodybuilding.com/For_Losing_Fat/m_111175/tm.htm