I recieved this question recently.

I personally don't schedule ads to run at certain times of the day. Mine run all the time.

Using that feature correctly requires you to have lots of data on clicks and conversions. The idea is that you spot a particular point in the day where you are getting more conversions, then you target that time of day.

If you don't know a specific time to target based on data, then it likely won't help.

The only broad timing decision you could make is if your product or service is geared toward a particular geographic region. For example, suppose your website is geared toward North American consumers. You could elect to run your ads only between 8am EST and 9pm PST which are the prime hours for American consumers to use the internet.

This would prevent your ads from running during prime hours in Europe or India. It might also prevent robots running overnight clicking your ads.

I would recommend controlling your spending with the daily budget. Set your campaign to show ads as quickly as possible, and let them shut off when the daily limit is reached. You can collect data on the clicks you do get and split test to improve your sales copy and get a higher CTR. Eventually that will reduce the CPC and allow your ads to run longer.

In addition, you can also improve your ads and landing pages to increase quality as my guide recommends. That will also lower your CPC.

I was recently asked the following question.

Try using "position preference". You can set it to only allow ads in the #1 position, which should be the "green area". Adwords will manage the CPC so that your ads appear only in that position. You can limit the daily budget to control costs.

Read more about position preference from Google themselves

http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=36482

Google has not released any information regarding acceptable keyword density. But, the accepted theory is that your maximum keyword density is 5%. That means if you have 200 words on your landing page, no more than 10 of them should be the keyword. Five percent is a high density and it's difficult to exceed that mark.

I generally look for a keyword density anywhere between 2% and 5%. That range is assumed to be good for Google SEO and Google Adwords.

I tend to make sure my keyword appears...

1. in the page url
2. in the page title
3. in the meta description and meta keyword tags
4. in the h1 tags

If I've done all four of the those, I find that I can have naturally written content without concern for keyword density and still get good quality scores.