Always use the ultrasound. You just never know what the anatomy is going to look like and real time guidance really increases the number of single pass lines. Every central line I placed in residency used ultrasound localization but then landmarks without realtime guidance for placement. Realtime ultrasound definitely helps.
Lots of saline. It's great stuff. Really helpful if you're having a difficult time getting into the vein. The needle and syringe will sometimes become occluded with clotted blood from prior attempts. Flushing both the needle and syringe until the syringe plunger action is smooth helps avoid getting into the vessel but thinking you haven't because you can't aspirate due to clot. I like to keep the fresh and used saline pools separate so there's always some fresh saline handy.
Making sure the needle is in the venous lumen. Taking the syringe off and confirming the blood is dark and nonpulsatile is key to checking that the stick isn't arterial. If it's venous and your proceeding I've found it helpful to slightly drop the angle of the needle (to avoid going though the opposite wall of the vein "through and through") and advancing it 5mm or so further to get the needle tip fully within the lumen. Sometimes, if just the bevel has gotten in just a slight release of pressure moves it out of the vessel and you can't pass the wire.
Passing the guide wire. Not infrequently you'll be able to pass the guide wire to a point that clearly is beyond the tip of the needle and then encounter resistance (if it doesn't seem to have gotten past the needle tip you may be out of the vessel and need to start over). In the case of having gotten past the needle tip and then encountering resistance, sometimes flipping the circular plastic holder that houses the wire 180 degrees (which rotates the wire 180 degrees) will move the curled tip into a more favorable position and allow you to proceed.
The skin incision. Key to a smooth initial dilator insertion is a large enough skin incision along the trajectory of the wire. I've found that holding the guide wire steady along it's natural exit trajectory and then making the incision along this same angle is very helpful. The cutting edge of the scalpel should be directed away from the artery (cutting edge facing medial for the femoral, lateral for the internal jugular).
Trying not to kink the guide wire. Again, I've found that holding the guide wire firm and steady along it's natural exit trajectory then with the other hand advancing the dilator from as close to the skin as possible reduces the chances of kinking. If the wire does kink and you are unable to advance the dilator further, try pulling the guide wire back a centimeter or so while leaving the dilator in place. This will pull the kink into the dilator and then using the same techniques as above you can often complete the dilation.
Lots of 4x4s. When the dilator comes out, lots of blood. Having a 4x4 ready keeps the field clean and minimizes blood loss.
The catheter is in but now a port won't flush or pull back. Most catheters rotate freely in the wings used to suture them in place. If a port isn't functioning try rotating the catheter 180 degrees by twirling it in the wings, this will often move the distal port off the vessel wall and allow pull back and flush.