Lifehacker has pointed out that the special Search operators can also be used when creating filters. This makes it possible to really pinpoint the emails that you are attempting to filter.
By default Google ANDs all data that you put into the filter fields. To use an OR condition all you have to do is put || between two strings (you can also just use OR). For instance to have a filter work that marks messages from firstname.lastname@example.org and email@example.com I’d just put: firstname.lastname@example.org || email@example.com in the From field.
There are a few other operators that you can use like a ‘-’ (hyphen) which will exclude those items in your search. Another useful operator is ‘filename:’ which you can find specified files. For example, if you want to put all PDF’s in a label called Files then simply put ‘filename:pdf’ and assign it to the label Files. These operators should help to simplify the whole filtering process.