If you pair up Avast Internet Security 7 on default settings with some common sense then you should have a very solid system protection.
Anyway here are some tweaks that Advanced users can apply to increase avast's protection:
1. Take full advantage of Avast Sandbox.
Avast Sandbox is a feature in avast! Internet Security 7 which allows you to browse the web or run another application in a completely safe environment. This is especially useful when visiting high-risk web sites, whether accidentally or deliberately, as the Web browser will be completely contained within the avast! Sandbox, preventing any damage to your computer.
The avast! Sandbox can also be used to run any other applications which you think may be suspect - you can run the program inside the sandbox to determine whether or not it is safe while remaining completely protected against any malicious actions that it may try to carry out.
I strongly recommend that you right click on your browser icon and select 'Always run in sandbox' so that you'll be completely protected while browsing the internet.
To run a new or suspicious program inside the sandbox you just need to right click it and select "Run in sandbox"
2. Increase detection level
You can theoretically increase Avast's detection rate by going into the Avast settings > Real Time Shields > File system shield > Expert settings > Sensitivity and increase the Heuristics level from Normal to High.
This should result in new threats being detected faster however it can also increase your false positive ratio.
By default Avast will not scan for potentially unwanted programs (toolbars and other crap like that) however you can enable this suite to detect and remove PUP's by going into Avast Settings > Real Time Shields > File system shield > Expert settings > PUP and suspicious files > check Scan for potentially unwanted programs.
3. Take control of the behavior blocker
Avast 7 was built with user friendliness in mind so it's not a surprise that the developers decided to let Avast take all the decisions instead of the user.
If you are an advanced user and aren't annoyed by some occasional alerts then you can go to Avast Settings > Real Time Shields > Behavior shield > Expert settings > Action to take > select "Ask"
According on my own understanding, Avast Firewall is known to be as "Silent Firewall" thus popup were likely user friendly and their BB is fine tune. Compared to Comodo its a HIPS and have a solid Firewall.