I will be 50 this year, and I started going to Dayton with my dad when I was 8. I probably have missed maybe 20 of them in my life since- if that. Here is a proven strategy;
1. If you aren't selling outside, forget Fridays. Most outside sellers aren't fully setup by Friday. Inside exhibtors are, but aren't staffed fully, or are still getting their ducks in a row. NO ONE is NEAR ready to deal.
2. Saturday is when it happens! Get there EARLY, preferably early enough to have breakfast in the Dayton area to unwind from your road trip, but get to Hara with enough time to park and be at the gate WHEN IT OPENS. The crowds will be low, the traffic wil be low, and most ouside folks are ready to roll, and inside too. But still, NO ONE will be ready to deal.
3. Start outside, and power walk the middle of the rows making notes of items of interest. It's early, people aren't dealing, and you can formulate your plan for the interesting stuff.
4. After that, head inside. It's hard to power-walk inside, but later it will be MUCH worse. Go to the smaller vndors first, then the big MFR's in the middle.
5. Time to go back outside, starting with the highest priorty items you saw. Deal as necessary, but be willing to walk away.
6. After that, it might be time to go to get a brat outside and /or a beer. Historically, I think the "best" food has been outside, and less of a crowd. MUCH less. Better air too.
7. Hit the lowest priorty items you saw, worknig toward the highest priority, to give them time to get dejected about taking the stuff back home to the nagging wife and the over-flowing garage.
8. Repeat 5 through 7 above as necessary.
Notes:
1. Pray for good weather. Rain dampens everything. One of the funniest things I EVER saw at Dayton is someone had the bright idea to "leaflet" the outside areas by a Cessna. The problem was they did it in the rain. The "leaflets" stuck together on the way down in telephone book-sized clumps of leaflets and went crashing throgh tents, thumped cars and broke antenna masts with everyone running and screaming. Also, there is no place to sit or hide outside in the rain, which makes the inside VERY crowded, almost to the point the air is fouled.
2. Don't waste your time returning time and time again to outside sellers that choose to set up stuff to sell, then cover it and never return. These people are idiots, and there are always more than a few.
3. Bring at least a small backpack or shoulder satchel to carry stuff. Keep a small foldup handtruck in your car in case you find something really heavy that you can't pass up. Don't be a hero and carry something all day- take it out to your car and return.
4. Don't forget cash, and bring small bills only- It's easy to deal that way and hard for the seller to round up.
5. Don't mind th crowds- that's what makes Dayton an event- the above tis make it more manageable.