As some people here already know, I'm a travel agent. Amongst other things, it means that every single day I have to deal with people who get themselves into all kinds of trouble because they were too stupid, too careless or too ignorant to do some very simple, commonsense things that require no special expertise. So to save my fellow Stargate fans some trouble, embarrassment, lost sleep and vocal chords damage, I decided to post a set of basic recommendations on how to avoid ruining your own vacation. Anyone who has additional tips is welcome to pitch in 
Note that these recommendations are mostly intended for people taking international rather than domestic flights.
1) Learn to spell your own name in English.
It's remarkable how unaware most people are on the basics of modern air travel, so here it goes: Your name on the flight ticket MUST be an EXACT match to your name on your passport. As in to the letter. A single misspelled letter may be a serious problem if you're headed to places such as the US, Ukraine or China; with two misspelled letters, it doesn't matter where you're headed because the airline won't allow you to board your plane. If you have an Eastern European, Russian or Asian name that can have a zillion spelling variants in English, I would advise you to give it to your travel agent in writing over email, not spell it on the phone.
Fixing a misspelled name in a ticket is not possible. At all. The GDS doesn't work this way. When you ask a travel agent or an airline representative to "fix" the spelling of your name in the ticket, you're basically asking them to make you a new reservation from scratch and scrap the old one. Most airlines won't agree to do it at all; those who do will charge between $50 and $100 for the operation, and you'll be the one paying.
In single-letter errors, a misspelling of your last name is more problematic than a misspelling of your first name, especially if it's your last name's first letter. A single-letter misspelling of your first name can sometimes be faux-fixed with an OSI- a special remark the travel agent inserts into your order to let the airline know the correct spelling. OSI does NOT change the ticket and does NOT formally oblige the airline to disregard the misspelling, but usually it works, and that's all you really need. OSI works for most destinations in Europe; it does NOT suffice for the US or China-bound flights.
If your travel agent tells you that you need to cancel your ticket and book a new one because of a misspelled name, there is no point arguing. Travel agents lose money on cancelled orders, and the process itself is a hassle we'd rather avoid, so we do not advise it lightly. If your ticket is a hopeless case, it's better to lose $200 in cancellation fees than to have yourself removed from the plane and lose your $1000 dollar ticket entirely.
(Just this week, I had a guy named Hanan whose name in the ticket was spelled... wait for it... Hassan. Flight to New York. Cancellation fee $240. He has no one but himself to blame).
2) Be especially careful when ordering online
Lots of people these days think they can outsmart the industry by ordering their tickets online. Sometimes you can indeed save money this way (not as often as people think; in case you didn't know, even if you're ordering online you're still ordering from a travel agency in most cases, and even if it's from the airline directly they still have a booking fee built into the price), but sometimes you can lose money. A LOT of money. Most of the catastrophic mistakes I see are in online ticket purchases. Misspelled names, wrong dates, wrong destinations, a flight to Budapest instead of Bucharest (with the hotel correctly ordered in Bucharest)- you name it. I would generally not advise an inexperienced traveller to order online, but if you must, be VERY careful where you click with that mouse. Keep in mind that after you get your ticket, any change will cost money.
Example: four months ago I got a call from a newlywed couple who went to Ireland for their honeymoon. They ordered their flight online, probably during an excited discussion or something, and accidentally clicked on the wrong date for their return trip. I did my best to help them out but there were almost no seats available on the Dublin-Amsterdam route, so the ticket change cost them $350 per person.
Note that these recommendations are mostly intended for people taking international rather than domestic flights.
1) Learn to spell your own name in English.
It's remarkable how unaware most people are on the basics of modern air travel, so here it goes: Your name on the flight ticket MUST be an EXACT match to your name on your passport. As in to the letter. A single misspelled letter may be a serious problem if you're headed to places such as the US, Ukraine or China; with two misspelled letters, it doesn't matter where you're headed because the airline won't allow you to board your plane. If you have an Eastern European, Russian or Asian name that can have a zillion spelling variants in English, I would advise you to give it to your travel agent in writing over email, not spell it on the phone.
Fixing a misspelled name in a ticket is not possible. At all. The GDS doesn't work this way. When you ask a travel agent or an airline representative to "fix" the spelling of your name in the ticket, you're basically asking them to make you a new reservation from scratch and scrap the old one. Most airlines won't agree to do it at all; those who do will charge between $50 and $100 for the operation, and you'll be the one paying.
In single-letter errors, a misspelling of your last name is more problematic than a misspelling of your first name, especially if it's your last name's first letter. A single-letter misspelling of your first name can sometimes be faux-fixed with an OSI- a special remark the travel agent inserts into your order to let the airline know the correct spelling. OSI does NOT change the ticket and does NOT formally oblige the airline to disregard the misspelling, but usually it works, and that's all you really need. OSI works for most destinations in Europe; it does NOT suffice for the US or China-bound flights.
If your travel agent tells you that you need to cancel your ticket and book a new one because of a misspelled name, there is no point arguing. Travel agents lose money on cancelled orders, and the process itself is a hassle we'd rather avoid, so we do not advise it lightly. If your ticket is a hopeless case, it's better to lose $200 in cancellation fees than to have yourself removed from the plane and lose your $1000 dollar ticket entirely.
(Just this week, I had a guy named Hanan whose name in the ticket was spelled... wait for it... Hassan. Flight to New York. Cancellation fee $240. He has no one but himself to blame).
2) Be especially careful when ordering online
Lots of people these days think they can outsmart the industry by ordering their tickets online. Sometimes you can indeed save money this way (not as often as people think; in case you didn't know, even if you're ordering online you're still ordering from a travel agency in most cases, and even if it's from the airline directly they still have a booking fee built into the price), but sometimes you can lose money. A LOT of money. Most of the catastrophic mistakes I see are in online ticket purchases. Misspelled names, wrong dates, wrong destinations, a flight to Budapest instead of Bucharest (with the hotel correctly ordered in Bucharest)- you name it. I would generally not advise an inexperienced traveller to order online, but if you must, be VERY careful where you click with that mouse. Keep in mind that after you get your ticket, any change will cost money.
Example: four months ago I got a call from a newlywed couple who went to Ireland for their honeymoon. They ordered their flight online, probably during an excited discussion or something, and accidentally clicked on the wrong date for their return trip. I did my best to help them out but there were almost no seats available on the Dublin-Amsterdam route, so the ticket change cost them $350 per person.