Background
I use a lot of vinyl tubing but dislike having to clamp it as is often necessary.  I also like joints that don't require clamps. so, I usually use tubing with an ID that's 1/16" smaller than the OD of whatever it's to be fitted to.  I typically use 7/16" x 5/16" tubing for joining to things that are 3/8" OD, 5/16" x 3/16" tubing for joining to things with a 1/4" OD and 1/2" ID tubing for things 5/8" OD.  Obviously, it's a tight fit and hence difficult to do.  Spitting on the parts to be joined helps and a tiny bit of Keg Lube works even better but, it's still difficult.  Also, even it you do manage to get the tubing fitted, it'll revert back to it's original ID after it's removed which makes reconnectable joins a chronic pain.  Examples of where an easily reconnectable, unclamped joint is idea is joining racking tubing to a plastic racking cane and joining different sized pieces of tubing together.  To expand the end of vinyl tubing....

How to Expand Vinyl Tubing
Basically, you heat the tubing and a mandrel, force it over the mandrel and let it cool while it's on the mandrel.  A piece of polished rod with a chamfered end makes a good mandrel but a piece of polished copper tubing with either a chamfered end or the end left by a tubing cutter will work.  I heat the end of the tubing and mandrel by placing them in a container of water that's been heated to around 150 degF.  Remove them from the water, shake off excess water and quickly force the tubing over the mandrel.  Grabbing the tubing with a dry rag and pushing and twisting the tubing greatly aids in getting the tubing on and keeps you hand cool.  Allow to cool then work the tubing off the mandrel.  A polished mandrel and a dry rag helps.    Try to do this while there's still moisture in the mating surfaces.

Fitting 3/16" ID Tubing to Cornie Keg Disconnents
3/16" ID tubing is recommended for shorter beer dispensing lines but the end of a cornine keg disconnect is designed for 1/4" ID tubing and the end is barbed to boot.   I fit the tubing much like the method above, only the end of the disconnect is used in place of the the mandrel and the joint can't be disassembled and reconnected (you have to cut off the tubing).  The joints are good to at least 30 psig and probably a lot more.

Clamping Small OD Vinyl Tubing
I like to use worm gear type hose clamps when I have to use clamps.  The problem is that even the smallest ones are too big for the 5/16" x 3/16" tubing I like to use.  What I do is fit a short length of reinforced or heavy wall vinyl tubing over the joint (if it's a tight fit, keg lube helps) and apply the clamp over than.  The downside is that the bigger piece of tubing will creep under the load (especially if subjected to a wide temperature range) and allow the joint to become a bit loose which necessitates tightening the clamp periodically.

Also one other thing I do you may wish to record in your info pages (if you agree that is!) I have had problems with the hose fitting the racking cane tight enough to not suck any air at the joint thus giving me airation. What I did to correct it was to cut 1/2 in off the hose and then take the long end and fold it as small as I could and the slip the short piece over it. This gets hard to get the hose round again but the perfect tool to do it with is the wire valve on my brass bottle washer. I stuck the end that loops around (like a U) into the hose and twisted it until it opened the hose up round. It's hard to get on and off the cane and bottle filler but it sure solved any airation I was getting.