First of all you should decide in which part of the world you want to spend your holidays and then look for rentals in that area. You should be able to know how many days you will need the property for and can plan about it accordingly.
You can browse through the website at the time you book for your holidays. Just browse through the 'Vacation Rental and then 'Housing' section and find a property that is within your budget and has other facilities that you are looking for.
To avoid the end-time hassle, you can get yourself registered on the website to receive regular updates from them within your specified area. At the time of registration try to get registered for the properties that offer pictures attached with description. Sometimes, some property owners offer online tours of the property as well.
Whenever you receive a property that has an interest for you, you can take the matter to contacting the owner. This is possible by emailing through the given link in the ad or else you can phone the owner, provided a phone number is given. Sometimes, people prefer to leave their phone number on the ad and you can contact them to inquire about the property even if you do not have to book immediately.
Since you know the conditions on which you are looking a property for, you can discuss it with the property owner at the time of inquiring about the property details. This includes the financial aspect and the number of days you want to rent the property for.
If you decide to book the property there and then, and the owner asks you for making an upfront payment of any amount, make sure you choose a secure method of payment. Do not make payments through some dodgy websites, as it can be fraud. Insist on paying through the method, which you think is more secure, or otherwise, ask to pay the money at the time you collect keys for the property.