Some basics:
1. Don't set your threshold too high. Set a budget so that you don't get a nasty shock after 1000 people suddenly decide to visit your site on one day.
2. Don't use common keywords. Competing with common keywords is a waste of time and money.
3. Focus on your niche. E.g. "camping in Kruger national park Berg en Dal camp" rather than "camping" or "iOS educational game development" rather than "game development". This will ensure a lower bounce rate as people find what they actually want (people don't click on your ad, costing your money, then leave after it's not what they expected).
4. Don't lie. Use keywords that are relevant to your product, service or content rather than adding as many as you possibly can. This will ensure that you only get the views you want, and Google won't get angry with you and ban you from AdWords -- do NOT spam your keywords.
5. Use Google to find keywords that work for you. Try typing your niche into Google and see what the recommended results are. You can either try to avoid these or follow them based on how many results each comes up with (less results is better, since you have a better chance at being seen more frequently).
