There are many factors to consider when placing any bee hive, however, Warre hives have some unique needs that should be addressed when deciding upon the final location.
While there are many "requirements" on the traditional "hive placement checklist," I think one of the most important factors to consider is ease of access for you, the beekeeper. The bees are adaptable, and can overcome just about any inconvenience you throw their way. If the location makes it difficult for you to enjoy the hive, and especially if it makes it difficult for you to work in the hive, this is a major issue. You will want a location that is free of obstructions on the backside of the hive, with at least 2-3 feet of space -- especially if you plan to use a Warre hive lift to add and remove boxes.
Warre are foundationless, and the bees build their comb perpendicular to the ground. If your hive is on a slope, the comb will be equally sloped. Make sure you place the hive on a level stand of some sort -- whether this is some cinder blocks or a fancy wooden contraption, just make sure it's level!
Early Morning Sun
While this doesn't apply to extremely hot areas, it is generally agreed upon that hives are more successful with more sun than less. If you have to choose between early morning sun and afternoon sun, go with early morning sun, as this will get the hive active earlier in the day, and provide them with more time to gather resources.
If you live in an urban or suburban area and you feel there is potential danger to either the bees or people, be sure to place the hive in a relatively concealed area -- preferably one that is fenced off. Many beekeepers who live in the city like to point the entrance of the hive toward a fence or a hedge
Ideally the hive will be placed in a location that is protected from harsh winds billowing into the hive entrances during the winter. Warre hives are inherently top heavy, and thus it is important to either provide a wind break, or straps of some sort to keep the hive from toppling over in high winds.
If you live in an arid region -- especially one where pools are prevalent -- this is consideration is more important. Bees need water to use within the hive, and they, being opportunists, will frequent the closest reliable water source, regardless of how inconvenient it is for you or your neighbors. If the closest water source is your neighbor's pool or bird bath, the bees will be more than willing to use them. If this matters to you, make sure you provide them with a shallow-sloped water source. Bird baths work very well!
Obviously if you plan to keep bees in your back yard you will have little control over the nectar and pollen sources available to your colony, but an important consideration nonetheless. We've had greater success with our colonies placed in urban and suburban areas, largely due to the abundance and variety of flower plants available in parks, gardens and yards. Rural areas, especially areas with heavy agriculture, generally have less forage available due to the use of mono crops, pesticides and fungicides.
The last, and maybe one of the most important factors, is whether it is legal to keep bees in your area. Many cities still outlaw beekeeping outright, or make the licensing process incredibly difficult for the beekeeper. Check your city, county and state laws prior to investing in a beehive and bees, and then make a decision accordingly. Keep in mind that a number of areas have antiquated laws explicitly banning the use of any hives but Langstroth or frame beehives. While I don't know of anyone being accosted over such silly regulations, it's still something to keep in mind.