How We Roll Winner
There's a number of things that you can follow in order to come up with a successful weapon. Let me tell you some:
Are you trying to make a weapon similar to Fantasy games or are you trying to create realistic weapons like plain longswords, broadswords etc.?
Get this cleared.
The outer shape of your weapon is what you start with. My preferred order for a plain sword is hilt(handle), crossguard(the meeting point of the hilt and blade) and lastly the blade.
Go into form detail. Is the hilt crooked? Is it straight? Is it long, extra long or very short?
The crossguard. How is it shaped? Like a dragon's mouth? Like a normal circle? A crescent moon?
Lastly, the blade. Research basic sword types. Or better, make your own. A blade curved towards one side is usually a single-edged blade, like a scimitar used by Persians. A Straight Blade can either be dual-edged or single-edged akin to a cleaver. As for the shape, anything goes as long as it is aesthetically appealing to you, good on the weapon's proportion and doesn't look so overly distorted that it cannot be classified as any kind of weapon.
Completely your choice.
Does the hilt have bandages? Is it plain? Does it have runes?
Crossguard, draw the dragon's eyes, the inner details on it's head. Or any other stuff depending on what you've made.
Blade, absolutely anything goes. It can either flow with the blade's direction or against it. It can be squares, curves, zig-zag lines or a beautiful combination of all these. Anything goes here.
In case of details, the more, the merrier. Just don't make it so detailed that you yourself get confused.
You can shade your weapon any way you want, if you are into shading. You can either shade with a light source in mind or you can shade along the details. You can put in a shine effect by leaving white spaces amidst your shading. (Don't overdo it). Leave areas with lighter shading or darker shading.
Remember to keep the tones flowing into each other. They must transition into each other brilliantly so that you can't notice the differentiating line between the 2 tones.
That's all there is.
Start with a faint pencil outline getting in the basic form and then work on it with a darker pencil. Once you've mastered it, you won't have to think of all these separately, the whole weapon'll just jump into your mind.
Mind the symmetry. A sword must be near-perfect in symmetry or it looks unbelieveably jarring. You don't need to achieve perfection here, just work on it.
Before trying out any weapon, check out how they actually look. Then play with it as you like.