My ad tips...
First, if you haven't done so already, you need to identify and break up your different groups within you target demographic. Almost any niche, product, or service will have a mixed demographic that can be split up and categorized.
In your case, you're promoting software. I of course don't know anything about this software, but for this example let's say it's a desktop office app, like MS Office. Assuming you have your keywords already (so we know what people will be looking for), now identify who will be looking for it. (who will be using these keywords). We don't wanna generalize them all and expect they are all one big, generic crowd.
Each niche is different here, but for this one it's safe to say that some of the demographic groups would be:
- students (most likely on a budget)
- technically savvy people who work from home and will be using it heavily
- less tech-savvy people who just need it for some basic work now and then
- small businesses looking for one or several licenses for employees
(you can probably think of more but we're keeping it simple here for the example)
Now we have identified our potential visitors and know who they are.
In order to write good ads, we also need to consider one more thing: in what state of mind will these visitors be when they are searching for MS Office?
They will be either in:
- Surfing mode - just surfing around the net, reading up on office application packages. At this point, they just know that they need an office application, but they may not know which ones are popular, which ones are out there, who develops them, etc.
- Comparing mode - starting to narrow down a few options that seem to match their needs. They want to know how they stack up against each other. Which office package has the best spreadsheet app? Which one gives the most value for money? Which one is most compatible with different document formats? Etc. etc.
- Buying mode - they have decided that MS Office is the one they want / need. Now they are looking for a site that has the best deal. They're ready to make a purchase but need to be told why they should get it through your site and not the competitor.
So we now have 4 categories of visitors, and we have 3 states of mind that these people will be in. Now it's your job to write up 12 different sets of ads (preferably 2 ads for each for split-testing).
Notice how I haven't mentioned wording yet? Well I think it's crucial to understand your demographic first - before you even think of what words to use. Many articles and books have been written about actually writing compelling ad copy. Your choice of words should reflect you are targetting, but also follow the AIDA principle:
Attention-Interest-Desire-Action (in that order).
Your ad copy headline should grab their attention. It's possible to do this with the copy body too with some creativity

The headline should also contain the keyword if possible.
Your ad text should then make the reader interested. This by playing on his/her emotions, desire, needs, and so forth. Check out some popular magazine / tabloid covers and note how they try to lure readers in to read more (and to buy their mag) by creating interest right up front. Lastly - make a strong called to action, forcing them to click your ad..
