Q: how the best way to clean up my mac to make sure its running fast

Please carefully read 25 Ways to Speed Up Your Mac for suggestions.

How to maintain a Mac

1. Make redundant backups, keeping at least one off site at all times. One backup is not enough. Don’t back up your backups; make them independent of each other. Don’t rely completely on any single backup method, such as Time Machine.

2. Keep your software up to date. Software Update can be set to notify you automatically of updates to the Mac OS. Some third-party applications have a similar feature, if you don’t mind letting them phone home. Otherwise you have to check yourself on a regular basis.

3. Don't install crapware, such as “themes,” "haxies," “add-ons,” “toolbars,” “enhancers," “optimizers,” “accelerators,” “extenders,” “cleaners,” “defragmenters,” “firewalls,” "barriers," “guardians,” “defenders,” “protectors,” most “plugins,” commercial "virus scanners,” or "utilities." With very few exceptions, this kind of material is useless, or worse than useless.

The more actively promoted the product, the more likely it is to be garbage. The most extreme example is the “MacKeeper” scam.

The only software you should install is that which directly enables you to do the things you use a computer for — such as creating, communicating, and playing — and does not modify the way other software works. Never install any third-party software unless you know how to uninstall it.

The free anti-malware application ClamXav is not crap, and although it’s not routinely needed, it may be useful in some environments, such as a mixed Mac-Windows enterprise network.

4. Beware of trojans. A trojan is malicious software (“malware”) that the user is duped into installing voluntarily. Such attacks were rare on the Mac platform until recently, but are now increasingly common, and increasingly dangerous.

There is some built-in protection against downloading malware, but you can’t rely on it — the attackers are always at least one day ahead of the defense. You can’t rely on third-party protection either. What you can rely on is common-sense awareness — not paranoia, which only makes you more vulnerable.

Never install software from an untrustworthy or unknown source. If in doubt, do some research. Any website that prompts you to install a “codec” or “plugin” that comes from the same site, or an unknown site, is untrustworthy. Software with a known corporate brand, such as Adobe Flash, must be acquired directly from the developer. No intermediary is acceptable, and don’t trust links unless you know how to parse them. Any file that is automatically downloaded from a web page without your having requested it should go straight into the Trash. A website that claims you have a “virus,” or that anything else is wrong with your computer, is rogue.

Because of recurring security issues in Java, it’s best to disable it in your web browsers, if it’s installed. Few websites have Java content nowadays, so you won’t be missing much. This action is mandatory if you’re running any version of the Mac OS older than 10.6.8 with the latest Java update. Note: Java has nothing to do with JavaScript, despite the similar names.

5. Relax, don’t do it. Besides the above, no routine maintenance is necessary or beneficial for the vast majority of users; specifically not “cleaning caches,” “zapping the PRAM,” “rebuilding the directory,” “running periodic scripts,” “deleting log files,” “scanning for viruses,” or “repairing permissions.” Such measures are for solving problems as they arise, not for maintenance.

The very height of futility is running an expensive third-party application called “Disk Warrior” when nothing is wrong, or even when something is wrong and you have backups, which you must have. Don’t waste money on Disk Warrior or anything like it.

Linc's #5 pretty much says it all. Lots of Mac users today have moved from the Windows world where 'bit rot' is a fact of life. The Mac's software architecture is nothing like Windows' and doesn't suffer from bit rot. Windows users are also used to performing the magic of disk defragmentation which is largely unnecessary for Mac users.

Its been my experience that newish Mac users think their Mac computer has become slower because they are used to their Windows computer becoming slower and the reasons must be the same. However, while they may be correct that the computer is slower than it used to be, the reasons are quite different. Generally I tend to see:

1) How much empty drive space do you have? Roughly speaking, you should avoid filling your hard drive more than 85%-90%. Software and the operating system create temporary files and when your drive gets too full these files cannot be created and that does tend to slow down the computer.

2) When you first bought your computer you probably didn't have any utilities and menuletes launching at start up and you probably tended to quit applications when you were finished. As you became more of a veteran you now have more startup items and keep programs running in the background. This can make the computer feel slower to launch and run.There's a program called Activity Monitor in your Utilities folder. Restart your computer,  launch it, and select the System Memory tab. Over the next couple of hours, look back at the Activity Monitor and look at the text next to the pie chart for Page ins. This tells you how often the computer has had to swap from virtual memory to real memory. If that number creeps up quickly it indicates you don't have enough RAM.

See:

Mac Maintenance Quick Assist,
Mac OS X speed FAQ,
Speeding up Macs,
Macintosh OS X Routine Maintenance,
Essential Mac Maintenance: Get set up,
Essential Mac Maintenance: Rev up your routines,
Maintaining OS X, 
Five Mac maintenance myths, and
Myths of required versus not required maintenance for Mac OS X for information.