1)Trendelenburg
2) Being a right hander, i've found it easier to cannulate the left EJV. That also allows you to leave the right side of the neck free for an IJV line later.
3) Once at the head end, stick your thumb under the clavicle. This stretches the skin and also makes the vein a bit more prominent. You can alternatively ask someone else to help you out with this move. Turn the patients head to the other side. You now have a nice taut neck, ready to be pierced!
4) Use a 16G cannula if you can. If the patient has a short neck, you may have to start higher up. The reason being if the cannula tip winds up very low, it starts to kink and you'll have to keep the patient's head in a particular position for a good flow. 20G cannulas are shorter, and you may not face this problem, but then.. they are 20G cannulas...
If your cannula tip is about an inch and a half above the clavicle.. you should have a good flowing line.
5) Many times, you would be inside the vein, but may not get the flash of blood in the chamber. So pull out the stylet and check.
6) If you aren't sure where you are, use a syringe to aspirate blood and work your way in.
Hope this helps !