A few Google Adwords tipps for you

Make extra campaigns per language.
Use extra setting for only 1 cent per click for display networks.
You sell a desktop app? Limit ad display to desktop computers.
People on a mobile phone are certainly not interested in your app.
Don't send everyone to your start page. Point them right to the page they want to go. e.g. tutorial page for people looking on tutorial ad.
Have lots of ad texts which contain keywords. Google prefers showing ads which match search criteria.
Create several google accounts. This makes it easier for accounting the different ad campaign costs for different products or services.