All-American Awards: The only way to get AA status is to compete at the NCAA finals. Top 8 = 1st team, next 8 = 2nd team, everyone else = honorable mention. Only the 1st and 2nd teams have the right to call themselves All-Americans. For cross country, only the top 40 are selected and there are no 1st/2nd/HM distinctions.
As for how to get to the finals, Buffalo.Rider is largely correct. Times/performances from qualifying meets are kept track of throughout the season. At the end of each season:
Indoor:
The top 16 individual and top 12 relay performances for each event are invited to the NCAA championship.
Outdoor:
The top 48 individual and top 24 relay performances for each region are invited to the prelims. The top 12 individuals and top 12 relay teams from each of the two prelims go on to the finals. Heptathlon and decathlon don't qualify via prelims; the top 24 of each go straight to nationals.
Cross Country:
CC selection is mostly team-based. There are 9 regionals, and all schools from each region compete at their regional. The top 2 teams from each region get autobids to nationals(18 overall). Additionally, 13 teams are selected as at-larges. Then the top 4 individuals from each regional not already on a selected team are chosen(36 altogether). Finally, 2 more individuals are selected without regard to a region. That brings the total to 31 teams and 38 individuals.
For example, NDSU's women's CC team placed 16th this year at the Midwest Regional. But Erin Teschuk placed 2nd. So Erin was invited to the nationals as one of the top-4 non-team selections. (she placed 116th there out of 253)
Here's a link to the USTFCCCA website(these are also the guys who officiate All-American honors): http://www.ustfccca.org/weekly-resul...fying-criteria
There are also links on that page leading to NCAA documents.