1) backing up backup your database and files from the present server 2) If the domain name is same after transferring to new server just upload all of your files create a new database fill that database with the data which you backed up update the information in the config file for the new database and you should be able to access your wordpress site on new server 3) in case your domain is changing you will need to change domain settings in your site options table which can be either done directly by editing the database (if you know how to) or by changing the site options to new site from the wordpress admin panel on present site (note once you change that information your wordpress site will become inaccesible on present site) and then follow step 2 P.S. - I have not tested the above mentioned methods this is all my opinion from my experience with wordpress
I have sold quite a few wordpress blogs and the buyers never complianed about anything becasue it is quite simple ..you would only come accros problems if you database size is very big otherwise it is quite simple just read up a few sites before you do it instruite has given a good short explanation.