In Dr Jason Nomura’s excellent blog takeokun.com he describes his technique to assist in viewing the needle during in-plane ultrasound guidance for vascular access.
The technique is described as follows:

• Obtain a sagittal view of the target vessel
• Stabilize the transducer and brace your hand. Then rock the probe to elevate the proximal section.
• Place the needle in the center of the probe (usually at the case seam) and under the probe footprint.
• Stop rocking the probe so the entire surface is again contacting the skin, the needle tip should be immediately visible.
• Advance the needle to the target vessel

Click the image below to go to the site and the demonstration video:

The “Ski Lift”: A Technique to Maximize Needle Visualization with the Long-axis Approach for Ultrasound-guided Vascular Access
Acad Emerg Med. 2010 Jul;17(7):e83-4