In essence, your advertisements are your means of communication with your prospects, and as such reflect your tone, your mannerisms and context of any relationship you may hope to create with them. It's all down to what you say and how you say it.
First you must have a strong headline - something that will grab their attention. Within just a few seconds your prospect would have decided that your advert is just junk or it has an interest for them.
By experimenting with different ad headlines you can find out what gabs people attention the most and use this information to your advantage. But don't stop there; you need make sure that the rest of the ad doesn't ruin a successful headline. Try and overcome any objections the prospect may have. If your product is expensive, explain why. If it will save them money, show them how. If it's a great offer, shout about it.
If you haven't got a strong offer then you need to create one. I often add in special reports and ebooks to ad value to my product. You could do something similar. You could even create a joint venture with another company to offer money off voucher for their service or products. This will cost you nothing but give a high-perceived value.
An astoundingly cheap and effective offer to make is through your guarantee - if you can double the trial time of your competitors, you reassure your prospects and minimise the risk they may feel they're taking. After all, most returns are made early on, by extending the trail time, you take no great risk on yourself, whilst giving yourself something to boast about. It's as close to a foolproof plan as you'll find in marketing, which is saying a lot, so there's no reason why you shouldn't exploit this as soon as possible.
When it comes to wording the advert, picture the person you are talking to. Who are they, where do they live, do they have a family, what is their income. If you understand the prospect you can craft the text to match their exact needs.