I've had a carboy cap installed on my racking cane "since forever" and I haven't had to "suck-start" a siphon in forever. That's my preferred method.
In general (this is not 100% accurate but for simplicity, we'll say it is), liquids like to equalize when a siphon is created. Given a working siphon with two vessels at the same level (on the same surface), the liquids will come to rest at very close to the same level in each container.
When you transfer from an elevation (say from the counter-top to a floor level vessel), the downwards column of the liquid is what creates a pull on the upper vessel (once the siphon is started). If (heaven forbid) your transfer hose is not long enough to reach the bottom of the receiving vessel, the maximum pull will be dictated by the length of the transfer hose. (We'll ignore friction in this case).
Starting a siphon from the same plan (say a counter-top) is quite difficult, because once the flow is started, it has to be stopped, sealed, and the end of the hose put into the receiving vessel. When you raise that hose to the top of the receiving vessel, if air is present in the line, there's a very high likeliness that it will release the column of liquid and that it will flow back into the originating vessel.
[Ok that's more than I ever wanted to write about siphoning. Ever.]
Bottom line: Use an auto-siphon, or use a carboy cap, and make sure that the TOP of the receiving vessel is lower than the BOTTOM of the originating vessel, and for good measure, make it 2 feet lower (or more).
M_C