You do not need to sort into bins or haul anything to the curb. A few small steps do make the job go faster, and faster usually means cheaper.
Decide what stays
Walk the space and mark what goes. A strip of painter's tape or a sticky note on the keep items works. If a whole room is going, say so and skip the tape. Pull out anything with paperwork, photos, or sentimental value before the crew arrives; you know your stuff better than anyone.
Get the accurate estimate
Send photos of the actual pile, from a few angles, including anything heavy like concrete, tile, or a full fridge. Junk removal is priced mostly on volume and weight, so the closer the photos are to reality, the closer the estimate will be to the final number. Mention stairs, long carries, or gate codes.
Disconnect appliances
Refrigerators emptied and unplugged, washers disconnected from water, and gas appliances shut off and disconnected by someone qualified before pickup day.
Clear a path
Move cars out of the driveway so the truck can get close, unlock gates, and put pets somewhere calm. That is it.
What you don't need to do
You do not need to bag everything, break down furniture, or carry anything outside. If you will not be home, say so when you book and work out access ahead of time.