The entrance to the area under your home is very important and should not be concealed!
An exterior entrance needs to be in plain sight, clear of trash, weeds etc. and securely covered. The cover needs to be tight but easy to remove in an emergency. If the cover is loose or the entrance is left uncovered animals will enter and you do not want to deal with skunks etc. under the house. The area around the entrance needs to be free of any objects that make entry difficult. Workers need plenty of room to enter, have tools available, run power cords etc. With a little creativity you can make the entrance an appealing area. Do not use the area under the house as a storage area. If something catches fire under your home it will be very difficult to extinguish. And remember that the worker needing access under your house is going to charge you by the hour to remove any obstruction or worse yet will refuse to do the work until you remove the obstruction.
Some homes have the crawl space entrance concealed in a closet. It may be covered with carpeting. Try to leave it clear of boxes, shelving etc. And leave a note where it is if you will be gone and someone will be watching the house for you. You do not want a plumber doing emergency repairs looking through all the closets to find the entrance if you are not available.
Please note: You will not have a crawl space entrance if your home was built on a concrete slab