Always have a list with you. And make sure it's updated. This will make your comic book hunting easier.This way, you know exactly what to look for when you're there. This saves you the trouble of buying something that you actually already have. There have been times when I went to con or a sale with a list that's not updated and I ended up buying some issues that I already have. So now I have duplicate issues of House of M #5, X-men #36 and 37, some Uncanny X-men issues and Soulfire # 4.
Lists are also a big help when you are shopping on a budget. Speaking of budgets...
Set a budget. But be prepared to go over it. Make sure you have your cash ready along with some extra. As much as possible, try to stick to your budget to avoid unnecessary purchases. When setting your budget, factor in other expenses like gas/ fare; entrance fees; meal allowances; etc.
Credit cards are evil. You already know why. It's easier to go over budget when purchasing with cards instead of real money, so only use your card if it's absolutely neccessary. Better yet, leave the card at home and just bring cash.
Dress comfortably. You'd be doing a considerable amount of walking and standing,so wearing the right foot wear is essential. Wear clothes that are made from soft and breathable materials like cotton and jeans. Screw the spandex.
Map out the venue. For safety reasons, it pays to know where the exits are, especially in case of emergencies. Also take note of where the fire extinguisher is should you see one; do not panic in case of an emergency. Other things to look out for are the location of food stalls, medics, and toilets.
Take a path. Don't go running off in different directions or else you'll tire yourself out. Look around and go to the first booth that catches your eye and start from there. When you're done with that, move on to the booth right next to it. Keep doing this until you reach the end.
There will be times when something is already reasonable priced, so in this case it's okay not to. Like the 20 peso comics of Comic Odyssey. Those are already a steal. Wouldn't you be ashamed to haggle?
The early bird catches the worm. Waking up early sure can be the the shits, but being early has it's perks. You get to paw all the merchandise before anybody else does so you have a bigger chance of getting everything you want.
Having said that, come closing day, most retailers would want to unload most if not all of their remaining stocks, and these often get hugely discounted so it's also worth it to wait a bit. I did this at a convention last year. There was a set of X-men Comics that I wanted, but I decided to wait until the last day to buy them. I actually asked the seller to hold it for me till the next day because I ran out of cash. I promised to return and get them the following day, which I did. Kind-hearted soul that he was, he did hold them for me, and even gave me a discount. True story. So remember this equation: Closing day = big discounts.
Don't hunt and shop on an empty stomach. Hunger will only cloud your judgement and may make you prone to impulse buys. Make sure that you've had a full meal before you go to the con so that you'll have lots of energy for going around. Take a break if you get hungry. Most cons have food stalls in the venue. Bring a bottle of water with you. You could get thirsty and dehydrated.
Compare. If you see a something that you like, and it's priced a bit high, hold back and do a little comparison shopping before you buy. Look around and see if someone else is offering it for a lower price. Chances are, someone is.
Bring a survival kit. Just bring what is essential to you and leave everything else behind. Aside from having my own shopping bag, I always bring a bag with me that contains some essentials like an extra shirt, a small notebook, a camera, my list, a pen, my salbutamol inhaler, a bottle of water, a packet of wet tissues and hand sanitizer. Hand sanitizers and wet tissues are essential because in my experience some of the boxes and comics are very dusty.
Bring your own bag. I always bring a bag with me to put in everything I buy, so that the seller doesn't have to bag the item for me. Doing that lessens the amount of wasted plastic in the end.
Bring a camera. And make sure the battery is charged full, and there's ample space in your SD card. But leave it behind if you're not even thinking of taking pictures. I always bring one with me because I want to document what happened at the sale/con, so that later I could share it here.
Go with friends. Wolves hunt in packs for a reason. Three sets of eyes and hands are better than one. Also, going around the venue can be boring and tedious, so having friends to do it with makes it much more enjoyable. If you don't have friends with you, make some. Smile and strike up a conversation with fellow con goers. It's always nice to have some company.
Follow the "Golden Rule". Be nice towards fellow con goers. Treat them how you would like to be treated.
Have fun. Enjoy the con! Don't stress yourself out when you don't get that prized Gundam, or if someone accidentally steps on your toes. It's supposed to be a fun experience.