I will be travelling to the USA in a month (by plane) but have found one-way flights are more expensive than return. Is there a good way to deal with this? So I can book the cheapest flight possible, when and where might I look to book?
Flying one-way with many of the major carriers is normally far more expensive than half of a return due to the way airlines price flights. That leaves you with three options :
If you're finding that the return ticket is cheaper than the one-way (not as unusual as you might think!) then you do have the option of buying a return and simply not using the trip back, however keep in mind that the one-way ticket will most likely have better conditions than the return. eg, the one-way - being a more expensive fare - will possibly be refundable and/or allow free changes (date, routing, possibly even cities). If there's any chance you're likely to use these benefits then it may be worth paying for the one-way - especially, if it's only a little more expensive.
If you do decide to go ahead with a return, keep in mind that the return leg doesn't need to be the same as the outbound. You might be able to book ZRH-AUS on the outbound, and a cheaper/shorter flight such as JFK-FRA for the return which may give a cheaper overall flight. Given that you're not going to fly it anyway, it doesn't really matter where you're "flying"! Try a few options and see what you can come up with.
Simple: Book a cheap return ticket, throw away the other half. You're not supposed to do this, of course, but unless you make a habit of it the airlines will not care.
Flights are cheapest when nobody wants to travel. Low season, midweek, departures and arrivals at inconvenient times, and awkward transfers all lower the price. Problem is, you're looking for a ticket for July (high season) with only one month's notice; it would've been better to book 3-6 months ago.