Okay so just want to ask a simple question,
Can you guys name some of the methods you would go about defacing a site (if you had too?)
My website is pretty secure I'm sure, but just to be safe, there is no admin page, and it is not SQL Injection vulnerable...
What other things do I need to look out for?
There are many different ways to answer this question.
Based on the information you've provided, I or the attacker would obviously want to look for some sort of listening service available besides apache, IIS God forbid, etc. I would first determine whether your web server is being hosted by a DNS or public domain, or by yourself on your own network, which i'm assuming is the case ?I would then look for zone transfers, do a dig, traceroute (all through proxychains, vpn), even nmap, and try to find a zombie to use as a decoy within your network, preferably a machine that wouldn't raise much suspicion in the logs, and pass as one of your own network devices.
The goal as an attacker/defacer/skiddie etc. would be to root the machine through SSH, and edit the index.html file directly, but i'm just jabbering here. SQL Injection, web flaws would be my first go to. But since you claim it's not SQL injection vulnerable (what makes you so sure ?). In the case SSH isn't listening, then I would look into other listening services, or possibly looking for google dorks, sqlmap, etc.
I would also be very interested what version of apache you're running, and how well you configured the .htaccess file, and try out some local and remote file inclusion vulnerabilities as syntax noted. How well the machine and / or the network is locked down in general would also be a question of mine.
Looking forward to other responses.