Over the years I have had many students attend these events. I also used to go "back in the day". Depending on where these are held, there may or may not be some things for them to do while waiting in line. Once they provided a nude model for students to sketch (much to the chagrin of some parents I might add).
Anyway here's my advice for what it is worth.
Get there very very very early (My students try to get there two hours early as the lines start forming early). Pick the school they are most interested in and stay in line for that school once they get through the open doors. They should prioritize their schools, and make decisions as to which schools they are willing to stand in line for.
I have my students LOOK at what other students are bringing in their portfolios (they report back what kinds of art they have seen). It will give them an idea on where their work stands. Most if not all representatives of the schools will be asking for the work to be from observation. They will evaluate the students' portfolios and give a critique. My students this year got "work smaller" and "you need more variety" as critiques, both comments they had gotten from me prior to going. The "work smaller" girl is not the best art student I have, but is very persistant and works large. I venture to say the "work smaller" comment means her work wouldn't scream "not the best artist" so loudly. The boy whose work got the comment "you need more variety" has a stubborn streak and is one who does as he pleases most of the time, regardless of the challenges presented by me.
Over the years I have gotten students accepted on the spot just with their portfolios, but not this year.
Prior to going my students and I organize their portfolios in a manner that we feel will peak the interest of the recruiter. That is to say we number the works from 1-15 (assuming they have 15 pieces, the numbering according to strength-1=strongest, 15th=weakest). We then organize their portfolio with starting with the #3 piece working up to the middle with #1 piece and ending on the #2 piece, alternating black and white, media and subject with the other pieces (never showing two figures next to each other, or two pencil pieces next to each other, or two color pieces next to each other, that kind of alternating). We then do a mock interview so that they are not caught off guard. The first year I taught in this school, when asked who their favorite artist was, my students very naively said "Mrs. Hasselman". I knew I had my work cut out for me, and still do!!