There is no restriction on US persons holding overseas real estate. The only requirement is if you receive an income from the property overseas you have to declare that income on your US tax return. If you pay foreign taxes and mortgage interest you might be able to deduct those costs from your taxes.
When you transfer money, the bank will notify the IRS (if it is $10,000 or more). This is something they do in the normal course of business. If you do something suspicious, like trying to structure the payments so that it is less than $10,000, then your bank will likely file a Suspicious Activity Report (SAR).
If you have cash in account overseas and all your overseas accounts add up to more than $10,000 at any point during the calendar year, then you will have to file an FBAR form listing the accounts and the maximum balance in those accounts for the calendar year. If the aggregate value is more than $50,000 then you need to file Form 8938 as well.
What should I look out for when making this purchase?
Nothing. You just need to ensure the appropriate forms are completed when you file your taxes.
Can I just do a regular transfer, or is there something in particular I need to do?
Yes. Your bank will probably ask you to fill in a form. There have been situations where the teller has asked the customer to structure the transaction so the amount is under $10,000 (to avoid the additional paperwork for them) which in turn resulted in stiff penalties on the customer... so don't listen to the teller if they ask you to do something like that! Depending on the bank, their systems may report the transaction automatically if they have all the information they need.
Secondly, if I don't rent it, so it will not provide an income ...., should I still be declaring it on my tax return?
I think the section of the tax return is 'income from real-estate' so if there is no income, then it should not need to be reported. Your tax professional should be able to confirm. If you are still a US person, when you sell the property, you will likely need to report the capital gain. This may also occur if you give up your US resident status in the future (see Expatriation Tax).