Scavenging and Finding Items in the Arena
Generally speaking, items and tools outside those assigned to or carried into the game by a character may be scavenged and found in the arena. There are, however, certain guidelines for this. Each game has a differing arena, and you should read the area descriptions carefully to make sure anything you want your character to find makes sense. A version set in a walled-off urban block, for example, is unlikely to have plentiful farm equipment lying around; maybe something could be found if a garden supply store is detailed, but it's hard to imagine a situation where, say, a pitchfork would be lying around. Similarly, an island abandoned in the late 1800s is not going to have much in the way of edible food or modern medicine strewn about, unless for whatever reason it has been artificially introduced by those running the game.
The universe also has a big impact on what can and cannot be found. As a general rule, SOTF-TV is most liberal about what is left for students to discover, as the executives know that creativity makes for good viewing, and the prospect of an escape is not as major a concern as in other settings. In Second Chances, meanwhile, the game lacks the widespread acceptance and societal and governmental complicity of the other games, making any disruptions not only a serious blow to the event but a potential threat to the terrorists' existence, and thus they take great pains to remove items that could prove a risk to the smooth function of the game. In all instances, there's a general nod from the game-runners to the idea that scavenged items should not be better than assigned weapons unless the assigned weapons are terrible. Limiting students' ability to upgrade their equipment without engaging their fellows is one of the ways violence is prompted.
You can almost always have your characters find innocuous, everyday items that are appropriate for the area. Rocks small and large in outdoor zones, chairs, tables, and the like in houses, and so on do not require any special communications with staff. Similarly, anything specifically noted in an area description is there for the taking. For objects beyond this but that aren't too high impact (tools that could be used as clumsy improvised weapons like screwdrivers, say) you can usually go ahead assuming it makes sense, but it's always safest to check with staff.
Actual weapons or items that are close enough to effectively be actual weapons (fire axes, convincing fake firearms, sharp chef's knives, etc.) are always removed from arenas unless specifically noted otherwise.
Finally, if you plan to use an item, no matter how innocuous, in some sort of escape attempt, please consult the further rules on that matter.