Are you using control groups?
Select some units, ctrl+1. now anytime you press 1 you will always select those units. Double tap 1 to move your camera to those units. Shift+1 if you want to add units to group 1. This works with all numbers across the keyboard 1-0 so I would encourage you to make several.
This also works with buildings. So you can have army one 1, your buildings on 2. Send your army across and without looking away from your army press 2 to select your buildings and make units.
If you have different types of units selected in one control group you and use tab to cycle through them. Terran example: if you have marines and tanks on 1, press one to select army, stim marines, tab to switch to tanks, and siege them. Likewise for buildings you can tab between barracks, factories, and starports or w/e buildings you have in the group.