have problems cleaning up my mac

Your memory which is RAM is different to your storage space on your hard disk, which I think is your concern about having too little of it free.

Regaining Hard drive space:

The easiest approach is to assume that the space has been filled up by your own files: documents, but also includes, videos you have downloaded, photos, music, pdf's, downloaded software. As these files have either been created or downloaded by you, you will know where to find them and these are the things to move or delete.

So look in your Movies folder, Documents folder, in the iTunes and iPhoto applications, for excess movies, photos and music that you can move onto an external drive, or burn to a CD, or delete.

If you delete anything remember to empty the trash to recover the space.

The quickest way to free some HD space is to use Monolingual and Onyx.

Monolingual will help you get rid of language packs which come installed with OS X and other applications, as well as hardware architectures, which you will most likely not need unless you are a developer. Removing the unnecessary language packs will also speed up the start time of your applications and minimize the amount of RAM they use.

Oxny can perform a variety of administrative task. I most often use it to clear number of different caches created both by the OS and applications.

The above should help you clean up your system, but you should also go through your applications and get rid of any that you rarely use or you do not remember when was the last time you used.

Innovadix, there in no need to delete applications, because they don't take up a lot of space. The person with the problem has a 500GB drive. A standard suite of all Applications would probably account for 4-5% of that. Deleting one or two would achieve little. It is not the thing to focus on, when from experience, the thing that mostly fills a person hard drive is different media like video clips and music downloads etc. Read my post for a simple but effective approach to this common problem encountered by many.

Read Apple Support Communities contributor Pondini's excellent

OSX Tips

Where did my Disk Space go?

You will find what roam already suggested, plus some ways of determining what is taking up so much space.

Monolingual can delete essential system components and has been known to break app updates.

How do I re install languages I deleted with monolingual

Monolingual cut English from my MBP. No way to type in password. Can't reinstall OS X.

Cache "cleaners" such as Onyx have been unnecessary for years. OS X performs its own administrative tasks so you don't have to.

If you are that low on disk space, deleting language and cache files amount to desperate measures. Do what you want, but the time to develop a backup strategy is before you seriously mess up your system, which you are certain to do if you resort to desperate measures.