In regards to knowing whether you're gonna but out or not...
Units will have SOPs as to different states of readiness. At each of those various states of readiness you'll have a matrix of activities that can or cannot be performed.
For example. If you've been notified that you're in a 5 minute state of readiness (which is that you'll be moving in either 5 minutes, or prepared to stand-to, etc.) you'll probably be told that you want to be within the confines of your immediate sub-unit (section, crew, etc.) and performing activities that are only essential ie. refilling your water bottle, taking a piss, throwing some CLP on your weapon, etc. Stuff like laying out your sleeping bag and setting up a hooch, or breaking out the stove to brew up are not permitted. If you're at a 20 minute readiness level, then other activities are prescribed, such as digging fighting positions, weapons maintenance, running the stove, setting up a hooch etc.
The other thing to always do is keep your stuff together at all times. When you're done using something, put it back in its place.
Here's a bit of an anecdote. Back in August of 2001 my unit, D Co. 4th LAR Bn. USMC, was up in Wainwright AB of all places on Ex. We were on our final FTX. and doing a force on force against a Gurkha unit that was over from the UK for their training cycle. Our company had set a screen line to picket the Gurkha's advance and the scouts were deployed from the vehicle in dismounted OPs. Sometime in the middle of the night the Gurkhas began their advance and were pressing hard into our positions. The order to withdraw was given to us just as a platoon of Gurkhas began to assault into our position. On hearing the order by the scout team leader to bug out, a young PFC of his responds "I'll be right there..." and on closer inspection the team leader noticed that this kid had a literal kit explosion around him. His entire ruck was unpacked and was dressed in his skivvies, . Apparently he missed the meaning of what had been passed in the op. order. The end result was this kid running down the hill towards the LAV with his pants around his ankles, ruck slung over one shoulder, sleeping bag being dragged in the other hand. As a good troop, don't let this happen to you (keep your sh*t tight) and as a good NCO, don't let your boys miss the meaning of what the task at hand entails.
If you're in a unit that doesn't bather to pass word as to what the situation is and what readiness level you're in, then I suggest you ask, otherwise you're gonna get f*cked when spending time in the field and having your ass hanging in the breeze.