How do you take a car alarm system out of Lock Valet mode?

SOURCE: car starter not working

look under the dash for a small silver toggle switch....this is a disable switch for the remote start portion of the system..you may have kicked it / bumped it with your foot, causing the remote start portion to be deactivated. Just flip the switch the opposite way and try again..
Also, there may have been a pin style switch installed under the hood...Check to see if it is bent or broken, if it is, simply disconnect it and insulate the wire that was going to it. 
This wire is used as a safety to keep the vehicle from remote starting while the hood is up..to keep people from being injured if the remote start is activated while the engine is being worked on. 
Have whatever shop installed the system replace your pinswitch if that is the problem.

SOURCE: viper auto alarm stuck in valet mode

u can open the drivers door if u have a 2 key remote just press lock aux lock again pretty fast and u should be great.

SOURCE: Need to turn the valet switch off On 1999 Nissan Maxima

Look for alarm Brain box and look for wires coming out black and red going to valet switch. to turn valet on turn ignition in ON position and press-switch or flip depending on the type of switch. If it a basic alarm just disconnect the main wiring harness to alarm box- unplug and the car should start. Good luck and thanks for using FIX YA

SOURCE: Car alarm goeoss car will not start

<Have heard that putting key into ignition in 'on' position and waiting sixty seconds for alarm to go off, then turning key off and back on will disable alarm. Haven't tried it yet.>

rweh is correct! Thank you! It worked for me!

SOURCE: uniden vs1100xr car alarm will

I had the same problem with my vs1100xr. The remotes for these (and other) unidens have a rolling code. Seems to me that either the remote runs out of new codes and cycles back to the beginning, or the alarm base unit somehow loses track of the codes. Either way, the alarm base unit stops accepting the codes of your remote, and so needs to be purged of its code tracking memory - reset, if you like. This is essentially the procedure for training the alarm base unit to recognise new remote (and forgetting old remotes).
This procedure is:-
1) Disarm alarm, or if in valet mode, take it out of valet mode (push valet button 3 times)
2) Turn the ignition on and off 2 times within 15 seconds.
3) Put the alarm into valet mode (push valet button 3 times) within 15 seconds of completing step 2. Alarm should beep, and remote training has started.
4) Within 15 seconds of completing step 3, push the button (#1) of the first remote you wish to use for the alarm. Alarm should beep, indicating acceptance of remote. Repeat for other remotes you wish to use - up to 4 in total. (Once the first remote has been accepted, you have all the time in the world to make the alarm learn other remotes)
5) Turn ignition on and off to end remote learning mode. Alarm should beep 2 times. New remotes have now been learned and previous remotes forgotten.

Some of these details may vary from country to country - who knows. If this doesn't work, I suggest that you contact Uniden in your country to obtain the procedure. Took me a few tries to get the timing right, what with the valet button hard to get at and having only 15 seconds between steps.