[Tinker51]

If you are going to do lots of them then the vise inserts that were posted above are indeed a very nice thing to have. To really do this right you need a special tool to assemble the hose ends. Go to aircraft-tool.com and enter the part # 2701 in the search, it's called a hose assembly tool (for some reason I cannot get this to put the link up today). You can buy just the one size or a kit with many sizes.
Now how to make one, tape it tight and use a chop saw to cut the hose, thread the collar on the hose end until it bottoms out (it is reverse threaded). Take the fitting and screw it into the hose assembly tool tight. Put a little white grease on the end of the tool and feed it into the hose carefully so as not to cut the inside of the hose with the fitting or you end up with a blocked hose. While pressing the fitting/tool in with the palm of one hand begin turning the wrench on the tool. On small hose (-3 and -4) it sometimes take a fair bit of pressure to get the fitting started. Tighten the fitting/tool until it is about 1/8" from the collar, remove the tool from the fitting, flush the hose with either air or solvoil. If the hose is short enough look through it to confirm that you did not gouge the inner wall with the fitting during assembly (just make sure there is no solvoil in the hose before you go and hold it up to your eye and the light directly above you. Ask me how I learned that one.)