Is there a general rule to go by when selecting the size of your crankbaits.  For instance, the Rapala selection comes in so many different sizes for each lure.  How do you know which size to use?  I hear fishing shows always using size 10 and above but they look kind of big (almost intimidating for fish).  Most of you will say the bigger the fish you're looking for, the bigger the lure.  In the lakes that I fish, I'm targeting Largemouth/Smallmouth from 12"-21".

Im not really good at picking out actual size but I have heard bass can eat other fish that are 75% the size of the bass.

I'm not sure how the patterns unfold on your fishery,but I have good sucsess starting out with small cranks like bandits and #5 or #7 shad raps in the spring.I tend to go over to the big deep divers after the spawn when fish move back out deep.Then in the fall I go to a DLN by Norman and it is really right in between.Hope this helps,but remember this probally will vary from lake to lake.

When I'm picking out a crankbait, size is not as much of an issue as running depth, action, and colour.

In general, a deeper diving crankbait is bigger than a shallow diving one (just look at the Rapala DT series).  As long as the crankbait isn't ridiculously big or small, I don't really pay attention that aspect.  If I need a crankbait to get down 15 feet, I'll be throwing a pretty big one because I don't have any small ones that will do that.  

while becoming more advanced over the past few years in bass fishing i have discovered that the bigger baits will procuce fish right before and after the spawn in the "transition" area, which is the spot where shallow meets deep, however ive only been fishing for a few years so what do i know

In the particular case of Rapala the size of the bait increases along with the diving depth capability of the bait.

What type of rod will you use when cranking? I use a St Croix mhm crank rod that is best for 3/8-1oz lures. I can throw smaller lures down to 1/4oz. If you use a MM or MF you may have to stick with 3/4 oz or smaller IMHO.

for cranks, depth, speed and vibration are much more important than size or color. Try sorting your cranks by running depth. Use the cranks that will get to the structure you want to fish. Experiment with speed and cadence. Experiment with different baits for different vibrations. Once you've found the correct depth, speed, vibration and cadence, then think about size and color. That's my system. There are bound to be many more ways to do this. This is the one that works for me.

Match the hatch!  Its a good place to start.

I like big baits.

Action, depth, profile, sound (vibration), retrieve speed and sometimes color are factors to consider. Smaller baits, I'm told, usually catch more fish.

I like big baits.

Matching the hatch seems logical. Matching the colors to native baitfish seems logical. Smaller baits may seem logical.

I like big baits.

I don't match the hatch, I don't care about the color as long as it's natural or dark or outlandish, but NEVER pink.

Did I mention, I like big baits?

Usualy size doesn't mater, but always remember to match the size to the fish and the season.

targeting Largemouth/Smallmouth from 12"-21".

Don't worry about the size of your fish, a 21" LM is perfectly capable of engulfing a 9" Slammer w/o blinking.

I think you talking about a size 10 husky jerk Rapala which is a 4" bait. You can catch most any size bass on a 4" jerkbait.

It depends on a lot of different things like everything else. If I want numbers I tend to fish the smaller sizes. If I would like to catch bigger fish I go a little bigger on the baits. Also in clearer water I go small to medium size. In murky water or at night  I always use bigger baits. The bigger baits have a larger  profile and displace more water making it easier for the fish to key in on the bait. Here's how I do it;

clear water smaller lures

murky/night bigger lures

big fish-bigger lures

more fish-smaller lures

Size has never been a major factor to me I look at how it wobbles as well as depth at which it dives. I do however mostly own big baits I belive in the fact that bigger baits catch bigger fish and as far as color I like to stay natural or dark. I have caught small bass on big lures so I wouldt be to concerned with them 12" to 21" bass your fishing for.

stick to what works for you.