Seven (7) Secrets To Knife Design
Let us begin with a simple means of looking at all knife designs: 

1. All Knives are either Symmetrical or Non-Symmetrical
The idea here is either even or uneven design. That's it. All knives, daggers and swords are of this nature. I have seen volumes written about blade types. What design is best, what type of point is most suitable. Clip point versus sheepsfoot, curved blades versus straight tanto-like blades. All absolutely just commercial flak to throw you off track. To create controversy and confusion. People thrive on opinion and controversy, they buy things they do not need in their confusion. Controversy and confusion make money for the cutlers and magazine publishers. The consumer is thrown to the wolves. Gimme dat money fool! See through this haze of BS and realize the truth of the two choices. "Even or uneven", choose what's right for the job. 
Common sense wins again.

2. The handle should match the task intended:
If the knife has a purpose (carving, bird and trout, tactical, etc) the handle (grip) should compliment the knife's mission statement. Awhile ago a great game knife came out. It was of the right design and size, the cost was well within reason. It was a handy piece to have on a Javelina hunt. But after just ten minutes of use the knife just chewed up my pal's fingers and thumb. You see, they put choils right there where your thumb sits. Seems to be a good idea, Those ridges provide traction under usage. But that was not the case at all. That thinking is conjecture. The real truth was that those "handy" choils acted like a saw blade under REAL use. No one had obviously ever actually used the knife for the purpose it was intended for or this flaw would have been immediately noticed and fixed. The grip is the only place you can touch the knife. Make it as user friendly as you can. Try to stay with natural products as well. Wood, bone, antler or leather works best for the handles. Keep away from synthetic grips if possible. Don't fall for the "durability" scam. Avoid micarta, dodge rubber, ditch the plastic and avoid aluminum. 

3. Function must remain primary in all designs: 
 I understand there is an "art knife" market. Art knives are beautiful and make the heart sing through their clever designs and colorful cosmetics. The makers and artists who cater to this part of the industry are to be commended for the incredible work they do. In saying that you should know that I deal only in function. My mind only works in those channels most efficient and practical. My mind see's to details and well thought out plans that must work in the situations they were designed for. My knives are meant to use, not look at. These are my opinions. And like assholes, everyone has one. So if you find issue with my opinions I understand, so go write your own article. Publish it and influence others, win fame and fortune forever!. But don't email me with such bullshit because I merely have an opinion. Step up mate. Tell us all how it should be or STFU! 
No matter the argument, function is primary. If the knife doesn't function as planned or as needed then perhaps another take on it is required. 

4. You Cannot have it All in One Design:
Land sakes alive! When someone makes their dream bowie-dagger-kuhkri clip point tanto hollow ground fish knife I just fucking gag! You cannot have it all in one design. If you try you often just crap up the original idea badly. Keep it simple, shoot straight to the heart of the trusted time proven designs and add your own little tweaks and modifications as desired. Creativity is good, but creativity gone amok is a frightening thing. It is ego, angst and bad thinking all rolled up into one package. You can make several knives, each unique and different from the others. But to combine those elements is risky and makes the knife either into an art knife or a reject from the cheap side of cutlery town. 

5. There is Nothing New in Blade Design: 
If you perchance have a moment to look through Burton's "Book of the Sword" you will encounter an innumerable array of designs, features and facts about every type of cutlery. There are pages chock full of various designs. Some sublime and others quite ridiculous. But one soon realizes that there really are no new knife or dagger designs. They were long ago thought out and brought to fruition by those who actually lived and died by the blade. We in our selfish ways only fool ourselves if we think we have thought of some new design or feature. So do not bust your brain trying to be special and different from the rest. I ask you "How"? How would you do that. Every one of us are simply just re-creators. The ego-based one's call it "theirs". They copyright and patent, the threaten and posture. All designs are theirs in some manner! Such ego is beyond my ken. Do your thing. Indeed make the knife. But stay rooted in reality. Too many in the cutlery business have caught the "It's all mine" bug. They have made a once cool industry into a shitfest with their ugly behavior.

6. Fixed Blade or Folding Blade (only two)
Here is another simple choice to make. The facts are that right now folders are selling better than fixed blades. But when most men are asked "what do you prefer to carry if you could carry any knife"? Is it "fixed or folder"? Most will not hesitate to fixed. But yet, laws and laziness dictate we carry folders. (sigh) The inherent liability of the folder (accidental closure) is always looming for those who use them. But even a fixed blade as strong as they may be can break and shatter. So, it's a 50/50 deal for most of us. But if you are making your own unit you must choose: Fixed or folder? There is a lot more detail and science involved when it comes to making a folder than there is to making a fixed blade knife. The folder market is more competitive than the fixed blade, plan your sales, articles and upgrades well. Who you know helps and adverts can bring your plans and your product. More goes into a successful knife than some vague scribbling on a napkin after the shot show. Do it right, dreams take flight. Do it wrong, a woeful song -

7. Cosmetics: Style or Panache:
Style, flare and eye catch lines or colors. This is panache, this is the cosmetic side of the end product. It is a small aspect, but it carries huge ramifications in the market place. Some of Microtech's awesome paint jobs on their automatic knives at first somewhat took the conservative cutlery industry by surprise. But their beauty was inescapable and soon the public embraced them as function and art in one. Well done Tony! 
Those stunning color schemes did indeed help sell the knives every bit as much as their fast in and out magic did. Your knife reflects you my friend. In your design allow the cosmetics to flow out. Ask others, get some input beyond yourself. Even if they know nothing about knives, people can still give you some real tips to improve your dream unit if you discern and listen with the good spirit. Do you desire the handle or the blade to be skeletonized? Or perhaps both eh? Should you put some swirly raised bumps on the handle for looks? Does it need a hole in the handle for the lanyard? If so, where will you locate it? Will the same lanyard throw off the balance of the knife? Hmm, so maybe yes or maybe no eh? Will the knife clean up easily? Oh hell yes this is a factor! Some knife designs lend themselves to easy cleaning. Others are bitch! Cracks, grooves and grunge go together. Yes, these factors are all part of that near final phase of design where you see to details that enhance the greater, overall design genius that you have hopefully put forth!