Let's see... Back when I started playing Pokemon in 3rd grade (holy shitnipples Ive been playing these games for more than a decade? But I digress) I'd only nickname some of them and gave them names based on their species like "Charry" and "Zappy." Later on in that generation and during the GSC generation, I gave them names I thought sounded cool, like "Cynder" and "Neon." (Keep in mind I was like, 10 or so)
When Ruby and Sapphire came out I continued that trend, though the names generally sucked less since I was older. When Fire Red and Leaf Green came out, I gave each Pokemon a name that was similar or had to do with what species it was, like naming an Oddish Audrey or naming my Snorlax Taft.
When DP came out I decided that I would name each of my guys the first name that came to mind, with results like "Meat", "Samson", and "Bitchtits". (okay I'm not positive about that last one but if I didn't I should have). I put in a little more thought when naming my starter (Pokey the Piplup) and my legendaries. (McLovin and Fappy were two that spring to mind)
Not sure what scheme to use when I inevitably get Heart Gold. Maybe dead presidents, or famous dictators or something.