The newest member of our troop, a young man with no previous Cub Scouting experience, just earned his Scout badge. It's technically not a rank and has only a few requirements. If he'd spent much time in a Cub Pack, he'd probably have earned that patch on his first day in the troop. There's a reason the requirements for the Scout badge are called Joining Requirements. The only one of them that can't be completed at the first meeting is the pamphlet exercises about preventing child abuse which MUST be completed with the new Scout's parent or guardian. Once that is done, the rest can be completed at a Scoutmaster's conference.
In our troop, as in all truly boy-led troops, most of the requirements for the early ranks can be signed off by higher-ranking Scouts and the rest by adult leaders. We try to encourage our younger Scouts to work with the older ones and we strongly discourage parents - even leaders - from signing off requirements for their own Scout. It isn't that we don't trust them, we just prefer that the boys reach out of their comfort level a little when seeking advancements.Your Scout will need to find out who can sign off each requirement and take responsibility for presenting his Boy Scout Handbook to them once he has mastered or completed each one. It is best not to wait too long after completing a requirement to have it signed off.
In our troop, the boys are also responsible for showing their Handbook to the advancement coordinator (me) periodically for recording in the Troopmaster software I use to track progress. Some troops keep a wall chart or paper log book. Whatever the means, that secondary record can be a lifesaver if a boy loses his book.
The early ranks are Tenderfoot, Second Class, and First Class. There isn't a specific time frame for earning each rank and boys should be working on requirements for them simultaneously rather than sequentially, even though the ranks have to be earned in order. It is easier, for example, to complete the First Class requirement to identify 10 native plants when the ground is not covered with snow -- even if the scout hasn't completed the Tenderfoot physical fitness requirement. Summer camp is a good time to complete the Second Class and First Class swimming requirements regardless of the Scout's current rank.
If a Scout has a permanent or long-term condition which would prevent him from completing one or more of the requirements before his 18th birthday, it is possible to request alternate requirements It's a fairly complex process which starts after a boy has completed all the requirements he is able to complete to the best of his ability.