Referring to text ads specifically, lets talk about quality and groups. Go here for a text Ad reference.
What makes up a text ad?
You need a headline, one or two description lines, a display url, and the actual url.
Tips for creating successful ads
Using this good reference I would advocate the following tips.
Be relevant- use your keywords in your headline and your description and your url! Take people to an ad and a web page that directly corresponds with their search.
Be specific- Tell what sets you apart or makes your unique. Why should they choose you over someone else? You can include prices, promotions, and exclusives. They may use this information to decide early on whether or not they’re buying.
Call to action- persuade them to visit or contact you. This is basically a sales pitch. Empower customers to take action such as purchase, call today, order, browse, sign up, get a quote.
Appeal to customers on mobile- realize that your ad may look different on mobile.
Experiment by creating multiple ads for a group and rotating them to see which one gets more clicks.
Google has some prohibited practices. Be responsible and honest about what you are giving and getting.
To get better ad results, try adding more keywords! Use more general ones, create a bigger bid, try out impressions, or experiment with different ad match types. You want your ad to be professional. Also don’t forget about how the landing page experience will affect your ad, so work on improving your site too. Try to stand out for the other ads in your niche. Use good formatting, proper grammar and spelling. Get to the point, as people take their impressions quickly.
CTR (click through rate) is probably the best measure of how successful your ad is. You can get a penalty if your ad is showing up a lot but no one is clicking on it.
Also learn how to use your Quality Score. This affects where your ad shows up and how often. you may not have to pay as much for a higher spot if you have better quality!