There are fundamental differences between Windows and OS X for its user interface, security model and design principle. If you’re new to OS X coming from years of using Windows, it might take a while to get comfortable working in OS X.
The best way when adopting OS X is not to resist the changes. You should adapt to Mac’s way of doing things, rather than bending OS X, installing utilities to make it behaving like Windows.
1. Natural scrolling
In OS X, when you swipe up with two fingers on the trackpad, the content moves up. This is Natural Scrolling and is the default behaviour since OS X Lion. Natural Scrolling follows the behaviour of iPhone/iPad and Apple touted it as the “right way” to be doing scrolling.
Natural Scrolling is the reverse of what Windows users have been accustomed to all these years. There are setting in System Preferences > Trackpad to reverse this behaviour but it is not recommended. Stick to the default natural scrolling and its a matter of time for it to feel natural to you.
2. Function keys
On Mac’s keyboard, the top row keys are for system controls such as screen brightness, volume level and media playback etc. Function keys are delegated for secondary purpose as you’d have to press and hold the fn key in order to access the F1, F2, F3…F12 functions.
You can switch things around in System Preferences > Keyboard so that you don’t need to press and hold the fn key to use them as function keys.
You probably would want to keep the default behaviour as function keys are not commonly used by Mac apps. Unless you’re using an app that makes heavy use of function keys, it is more convenient to just use the keys as system controls.
3. Windows software
It is common for new Mac users coming from Windows to install a copy of Windows on their Mac, either using a Boot Camp partition or a virtualization software such as VirtualBox, Fusion or Parallels.
Mac and OS X is now a common platform. Many apps and games that were Windows only are now making it to OS X or have a web-based version. You should switch to use Mac or web-based equivalent apps as part of moving to OS X. Unless you have an enterprise app that is Windows only, you should be able to move off Windows apps and remove Windows completely from your Mac.
4. Anti-Virus software
It is not uncommon for Mac user to not have any anti-virus software installed. OS X includes everything it needs to help you to protect it from viruses and malware. With common sense and caution, you can be free from ill-intended software on your Mac without an anti-virus software.
There is still a debate if anti-virus software is needed for a Unix-like operating system such as OS X. Anti-virus software gives you peace of mind but it has the potential of slowing down and destabilise your Mac.
You probably should consider an anti-virus software, but it should not be the first software on your mind and on your Mac especially if you’re a savvy computer user.