The first humans to Mars need to be highly trained teams, obviously. A good model for the first crews is the Special Forces Alpha Team. Alpha Teams are made up of 12 members: 1 Commander, 1 Assistant Commander, 1 Operations Sergeant, 2 Communications Sergeants, 2 Medical Sergeants, 2 Weapons Sergeants, and 2 Engineering Sergeants. Also, Alpha Teams are assigned to certain environment specialties such as mountain, ground mobility, scuba, etc. All members of the teams cross train each other in their specialities. Training is intense and focuses on working under extreme life threatening pressure, fast thinking, and an ability to improvise with limited resources.
This can easily translate to Mars exploration teams (METs?). A strong leadership structure will be necessary. As far as we know there will be no need for weapons specialists, but there will be need for medical, science, engineering, and operations specialists. Since there is no guarantee all will return alive, cross training will be essential. METs can also be specialized (as a team) for various terrains on Mars … Mountain, Valley, Lava Tubes, Polar, etc.
We could send multiple 12 member METs to various places on Mars, generally during the same time. These people will be our vanguard, our trailblazers, and many of the heroes that will become immortalized in Mars lore.