I like to use first names (or forename) to cite the work of others. It has become even more relevent when I found that somebody working in my field shares my initial and surname.
However, this is not the most common practice and in many cases, I do not know the forenames of the people I would like to cite.
Do you know of any pratical way to find these information ?
I usually resort to Google and Google Scholar search but that does not always solve the issue and can be time consuming (considering it is a detail).
In addition to other excellent answers, I would like to make a suggestion for you,
Find the author's e-mail address and then send an e-mail to ask the author's full name.
If the author replies, you get the answer. If the author never replies in a reasonable time period, find the author's professional name as suggested by others or use the name that appears in the paper you are citing.