Warning: You should only use the below information if you have been instructed to apply micronutrients in a specific dosage by one of the soil test interpreters on Bestlawn.Info
There is no magic to the application of micronutrients to your lawn or garden, but micronutrients are items used in very small amounts (from less than a tablespoon up to several tablespoons per 1000 square feet, depending on the specific micronutrient), and therefore should be applied with much more caution than macronutrients.
The best way to apply micronutrients is to combine them with a "vehicle", which is a safe, granular substance that can be applied at any point in the year that the ground is not frozen. It is for that reason that we recommend the use of Milorganite (or equivalent) - this product has the appropriate grain size and can be applied at any reasonble rate during any season.
Most of the time you will get instructions to apply micronutrients in tablespoons per 1000 sq ft. Realize that a bag of Milorganite covers 2500 sq ft, and therefore you should do the multiplication with a factor of 2.5X if you will be applying the micronutrient to 2500 square feet of lawn. You can raise the amount of Milorganite, but don't change the amount of the micronutrient per 1000 square feet of application.
The best way to mix the substances (Milorganite "vehicle" and one of more micronutrients) is to pour a bag of Milorganite into a wheelbarrow. Sprinkle half of the micronutrients (reserve the rest for a few minutes) over the surface of the Milorganite and then "mist" them with a handheld spray bottle very lightly. This causes them to stick to the Milorganite. Milorganite smells terrible if you get it really wet, so don't use any more misting than necessary to get a touch of stickiness. Mix with a large shovel for 5 minutes (all the way to the bottom), and then repeat the mixing process with the half of the micronutrient(s) that you reserved.
When it is thoroughly mixed, shovel it into a spreader and apply it. If you have adequate time, apply it at half the rate in one direction, and again in the perpendicular direction - this provides more even coverage and fewer "missed" or "overlapped" areas.
When you are done applying the Miloganite/micronutrient mix, water it in with at least 1/4" inch of water - this avoids the possibility that the very uppermost regions of the soil get "shocked" when a very light rain or heavy dew occur, while the deeper soil gets nothing.
Do not re-apply micronutrients on a regular basis. They should only be re-applied when a soil test indicates that they are below the proper levels. If you are unsure about the proper levels, post a question on the Soil Management and Composting Forum.
As always, ask questions on the Forum if you are confused by any of the above information...