IE... Not too much protein at any one time or too many simple carbohydrates.
Eat 6 regularly spaced meals that each contains 1/6 of your total calorie intake for the day. Of those 6 meals I have found that 2 can be a protein shake which helps to keep your total protein intake where you need it to be if you're training but not to much all at once. Remember beyond about 35 grams at any one time and it gets hard for your body to process. This number is also widely debated but most trainers feel its best to divide your protein intake evenly throughout the day so for most people 30-35 grams at any one time would be on target.
People will argue what is the correct amount but if you stay within .75 - 1.2 grams per lbs. of body weight you will be in the target zone for training and growth. This does not mean avoiding carbohydrates. Stay with Polysaccharides (complex carbs, starches, fibers) which come from whole grains, vegetables, nuts, some fruits and legumes. Additionally, complex carbs will not continually 'spike' the insulin levels, you'll send less signals to store fat to your body. Avoid processed sugars with your meals candy, table sugar, syrups (not including natural syrups such as maple), regular carbonated beverages, refined flours, and most processed foods.
Unrefined grains are also rich in fiber, which helps your digestive system work well. If you're not eating enough fiber it may help if you increase your fiber intake along with your protein supplement. I would add a scoop of MyoFiber by Muscleology to your protein shake. The combination will work well and not upset your stomach.
A good generalization is to have each meal portioned about the size of your fist with 1/6 of your daily protein intake in each meal. If you follow the 2 other rules about what to eat you will get the proper amount of carbohydrates etc...
The quality of the protein you're supplementing with may also play a factor in how well it's tolerated in your system.
Optimum is one of the most well respected names in the industry. Almost every professional Bodybuilder has at one time or another endorsed their products. The consensus seams to be the 100% Whey Protein is the one to go with. It won the supplement of the year for 2005/06/07/08 which is saying a lot.
I hope this helps, take care.