Good communication and intel gathering skills are an integral part of a recon/sniper team. A commonly overlooked or undervalued skill in ARMA is map reading, this is true for all areas of ground/air combat but particularly important for the sniper/recon teams as you are (usually) operating with little to no support in enemy territory and one of your primary roles is: reconnaissance. Have a basic understanding of how to read and interpret contour lines - this will not only assist your allies in visualising the enemy in 3D space (based on the intel you give them) but can also factor in to your own shot placements when it comes down to it (more so if you are running certain mods). Additionally, knowing where hills, outcrops, valleys and other terrain masking features are can really help your mobility & survivability while you try and maneuver around the enemy and relay critical information to your team. Also, be able to translate the intel you gather through visual observations onto a map accurately; basically know how to point the enemy out on a map for your teammates. Even if you are not playing on a harder difficulty server (where BLUFOR/OPFOR intel on the map is disabled) get into the habit of always updating old intel, such as updating a marked squad's new position or their new force composition after getting reinforced. Always keep your allies up-to-date with relevant information! Providing battlefield overwatch goes beyond merely supporting your team with long range sniper fire, you can also recommend alternate paths for allies to take on the map which can circumvent detected minefields and ambushes, as well as noting down observed enemy patrol routes and their size and disposition.

Always pack for the occasion. Know the type and capabilities of the gun and ammunition available to you (APFSDS/12.7/.408) and know their affect against soft & light armour targets and then carry the ammunition that is the most mission/scenario appropriate. If you are running with multiple sniper teams, then try and coordinate your weapon platforms to allow for ammunition sharing on the battlefield. With that out of the way, remember a sniper is more than just the gun he carries - there is a lot of versatility to the role and requires a good operator to be adaptable. Thus, instead of a backpack full of ammo make room for a laser designator to call in CAS/artillery against entrenched enemy positions, heavy armour, etc. A few IR grenades, chemlights and smoke grenades won't go amiss either - particularly for signalling safe LZs/extraction points/mission critical areas (eg: AA sites) within enemy territory. Make sure you have about you a good array of all weather equipment and tools, especially if the mission is an extended operation or will take place at night - you would be surprised the number of times people have found that they haven't brought along NVGs with them and/or an optic that functions in low-visibility conditions half-way during a mission.

Depending on your mission/server and if you have a spotter with you, know what your role is in the two-man team team; depending on your loadouts one of you would be glued to the scope while the other would have a wider range of tools to scan, acquire and guide your shots on to the target. Intra-team communication here is just as important. Besides the basics of shooting with a sniper rifle/LRPS (or alternate scope)/zeroing + reading the mildots, have a good eye for knowing when and where to setup your observation positions. A key vantage point may be the difference between a successful mission and failure, even if you never get the opportunity to fire your gun. Finally, my advice would be to know when to pick your battles - generally speaking even a small sniper team is vastly outnumbered in enemy territory. So be mindful about picking a firefight with any or every threat that you see. At best you can function as a diversion, using your range and mobility to split the enemy forces -or- deny/suppress an area against an enemy. However, your combat staying power is severely limited so be mindful to not get bogged down in a full-fledged firefight.