This will be my fifth Bronycon. It was my first big convention ever, too, in 2013. It is a sensory overload but in a great way! There are huge crowds of attendees all over, but there are places where traffic is very thin to hang out as well. In my experiences, the most important things I have learned would be...
Don't go alone if you're on the street. It's safer and much more fun, plus if your phone dies it's good to have another person. Also, being in a group in the con itself is much more fun. Also BE CAREFUL at night. It IS a city and there are often unsavory characters out and about if you turn down the wrong road. Don't wander at night - stay close and in groups.
Learn the layout of the convention center and panel rooms before the con. It's a huge facility and you'll save a ton of time if you know where and when to go well ahead of time. Also learn the layout of the streets around the convention center. Baltimore is not a good place to be lost. There should be maps with the con book you get at registration.
Arrive at least half an hour early for all panels. They fill up FAST.
Same for autographs. People line up way over an hour in advance to buy vouchers. Always expect lines to be really long unless you get there super early.
Please learn from my mistake and wear comfortable shoes that won't hurt your feet - you will be doing a LOT of walking at this particular con.
Share the room cost with as many people as the hotel will allow. Splitting the hotel cost will save you hundreds of dollars. You'll probably make new friends that way as well.
Try to eat before or after typical meal times to avoid long waits at local restaurants from the con crowd. If you like sandwiches, you'll be eating at Jimmy Johns a lot. I recommend it.
Make sure everyone has a room key. The walk back to the hotel is very long and you don't want to have to go all the way back to let someone in.
Speaking of hotels, try to get a room at the Hilton or Mariott. Those are the closest and there are always convention attendees to group up with. There's safety and fun in numbers.
Pack for warm weather. It's very hot and humid in Baltimore in August. It has also rained multiple years I've been.
Make sure everyone in your group has contact information with each other. I recommend a Skype or Facebook group chat, as my group has done most years. I can't tell you how annoying it is to have to wait for someone who can't be contacted when you plan on going places as a group.
If you have a portable battery charger for your phone, I highly recommend taking it. It is very important to have a not dead phone for communication. If nothing else, bring a wall charger. There's no guarantee you will be able to find one at the con.
Don't be afraid to talk to fellow attendees. In all my life I've never met a friendlier or happier bunch of people, and I've made so many friends just by random talking. Yeah, there are some grumpy folks here and there, but for the most part conventions are the friendliest places on earth.