Run instances minimally - While instances are fun, and provide
AoC gold and items, they tend to be time consuming in the long run, while you looking for members, going to the instance and waiting for everyone to arrive, you could have gained a lot of xp. If you in bad need of gear upgrades, run an instance or two, otherwise, try to avoid them.
Turn on the quick
AoC gold quest text option - Look for the instant quest text option in the option menu and toggle it on. If you played the game before, chances are you know all or most the quests already, and don need to spend the extra minute or waiting for the text to finish popping up.
Minimize travel time - If there a buy
AoC gold quest you need to turn in at a specific city, consider it importance relative to your overall XP/hour, if you can turn it in later, wait, if not, try to turn in multiple quests there at the same time.
Use combos to quickly kill mobs - When grinding it can be tempting to put your character on auto-attack, and then rinse and repeat, however, to be time efficient it best to test your character abilities and find out what combination can bring down a mob the fastest, even a second or two off the top can mean thousands more xp/hour.
Buy
AoC gold Ask for help - If you can figure out what to do, don be afraid to ask for help, consider joining a guild or asking someone more knowledgeable with the game for help, however, politeness is key, since some people rather not be bothered, it best to ask generally rather than messaging random people you see.
