Take this blue one with breakfast and this one with dinner. This powder you have to take away from food and this one you need to take while eating spinach, standing on your head, 3 minutes before you fall asleep. Supplementation can be ... confusing, to say the least.
Here are some quick tips to clear away some of the confusion:

As a general rule, vitamins and minerals (especially the fat soluble vitamins D, E, A and K) need to be taken with food. "Taken with food" means just that, try not take them before your food or at the end of the meal but in the middle, with the meal.

The enzymes that are being secreted throughout the digestive tract while you eat are meant to help break food down to be better absorbed when they get to the intestine. These enzymes will also help to break down the supplement, allowing for it to be better absorbed and better utilized within the body.

As a general rule, herbal remedies should be taken away from food. Your Greens supplement can be included in this group, as well. These supplements are best taken on an empty stomach, meaning either a 1/2 hour before food or 2 hours after.

Here are some specifics on a few of the more 'pickier' supplements:

Iron
Best absorbed if taken with vitamin C, but must be taken away from both zinc and calcium, as they reduce the absorption of iron. Post menopausal women and men do not need to supplement their iron, unless directed by a healthcare physician.

Calcium
Takes away from iron and fluoride, as they reduce absorption. To maximize absorption, take only 500 mg at at time, with meals and ensure you are getting adequate vitamin D and magnesium as they both aid in the absorption of calcium. One exception to the rule of "with food" is the commonly prescribed cal/mag supplement that is often recommended before bed because of the added benefit of promoting relaxation. If you are taking a calcium supplement away from food, it is recommended you take calcium citrate as it tends to be better absorbed than the carbonate form.

Probiotics
There is a lot of question about whether a probiotic supplement should be taken with or without food. Although better to get it in if not at all, most heath care professionals recommend you take it away from food – either first thing in the morning, or just before bed.

Fibre
Fibre may alter the absorption of many supplements and medication. The best rule to use with a fibre supplement is to take it away from other supplements and medications (2 hours if possible). It is also very important to increase your water consumption when increasing fibre.

Zinc
Zinc supplements can reduce copper levels, as well as alter the absorption of magnesium. Make sure your multivitamin includes zinc and copper and and ensure your zinc intake stays below the recommended 40 mg/day (Adults).

Interactions between a number of medications and vitamins/minerals exist, most of which will effect absorption and therefore utilization in the body. Always consult with a healthcare professional when starting a new supplement regime to ensure you are making the right choices for your individual needs.