"No soldier shall, in time of peace be quartered in any house, without the consent of the owner, nor in time of war, but in a manner to be prescribed by law."
United States Constitution
This one is very simple and straightforward. All it is saying is that the military cannot force any person in the United States to utilize his or her private residence for the purpose of housing a member of the military.
If an entire regiment were to show up on your doorstep requesting a place to stay the night, you do not have to let them into your house. You are free to tell them to move along and let them rent out the Motel 6 down on the Interstate. This applies in both peacetime and in war.
The clause "but in a manner prescribed by law" indicates that the soldiers living arrangements will be specified by law and will not include the use of private residences. This is why we have military bases operating both in the USA as well as abroad. Military housing is provided for the soldiers in the American Armed Services. The United States honors the Third Amendment even when the military is stationed overseas. This is a courtesy America chooses to extend to the host nation in order to ensure peaceful relations with that nation.
Allowing for the fact that the Bill of Rights was written in the 18th Century, a more modern wording would sound like this:
"No citizen of the United States can be forced to allow any member of the United States Military to live in his or her private residence. For a soldier to live in the private residence of a civilian requires permission from the civilian and the civilian retains the right to refuse such accommodations. This applies in both peacetime and in war. Residence for the members of the Military shall be provided by the Military as prescribed by law."
That took 78 words to restate what the original 32 words said. There is something to be said for brevity, don't you think?
Next installment the Fourth Amendment. Gather all of your liberal friends because this one will make their skin crawl, I guarantee it!