Make sure you know what you are getting for your cheap air flight, even food could be a problem if not provided. This is not that important on a short flight but on a long flight not having a meal could cause great discomfort.
The ways that airlines get the price of flights down are generally outlined in advance when you buy your ticket. It is generally in everybody's best interest to understand the conditions of your flight so that you aren't shocked latter.
Don't forget cheap air flights are a game of giving and taking so don't be willing to give up any more than is necessary just to save you money.
One way the airlines attain cheap air flights is by reducing how much baggage you can bring. Sometimes people are so happy that they were able to find cheap air flight that all they see is the in-flight meal is not offered and they figure they can live with that.
The Convenience and comfort of your flight can be severely affected by the rules of a cheap air flight. The baggage requirements need to be understood with your discounted air flight so that there are no rude surprises at the airport with to many bags, and you are refused or even charged unrealistic fees.
Multiple stops on your flight
A trick airlines use to offer cheap air flights is to break it up into lots of little flights. For example to get to London you may need to go via India, instead of direct and this simple detour could be most inconvenient. Some people don't mind but many do.
Always check on the connecting flights before you commit to a discount air ticket. Chances are very high that you will be visiting a few other cities before you finally get to your destination.
If you are flying non-stop from Sydney to London do not underestimate the in-flight meal. If you can't go without a meal for 10 or more hours then there may be a problem and discount air travel may not be for you. So know what to expect with cheap air flight because you need this information to be prepared.