Well, if I'm going for everything, I use a normal pick to dig 4 blocks down, make a 5x5 room 3 high, repeat until I hit bedrock (laying ladders as I go). I widen the bottom room to 5x5, slap down a workbench (or tool station) & some chests.
Assuming TiC is installed, I break out the hammer and dig out a 55x55 square. I use a pick to get the extra ores out of the floor/walls/ceiling. I go up to the next room and do it again... I hate leaving ores behind. For starters, I just use an iron hammer with max haste, mainly because it's easy and cheap to repair. Eventually I upgrade to something better.
If I don't have TiC, I instead do a branch-style mine based off the same 5x5x3 rooms... I extend the bottom room north/south by 25 blocks (making it a 5-wide 55-long hallway), then dig a series of single-wide tunnels (3 high, I hate being cramped) for 25 blocks east and west of the main hallway, putting a new tunnel every third block. On the next level up, I rotate the pattern 90 degrees (extending the original room east/west, with the side tunnels going north/south). I just keep flipping the pattern back and forth all the way up.
Like Shneekey, I prefer to mine with Silk Touch & process the ores later. Even if I don't have TE installed, they stack easier and I can just use a fortune pick on them once I get back to the surface.
I prefer to let a quarry or turtle do that for me while I go explore mineshafts & ravines. Magic World 2 is killing me with no automated miners. I guess I need to look into Blood Magic for that.
