If possible place components with same orientation and alignment
If possible place IC’s with with same orientation with “snap to grid” on in you PCB design software. This will help to eliminate possible mistakes when soldering or when inspecting a component.
Check size of footprints and design before sending your design
Printing your layout with a 1 /1 scale is always a good practice. Place each component on top of the paper to see if they match to your footprint, also check mounting holes. Sometimes datasheets may have errors or your distributor can send parts with a different package.
Use test points to make important nodes accessible for easy controlling
There is nothing more annoying than trying to touch the tip of your oscilloscope to measure a signal without making a short connect while trying to figure out what is wrong with your prototype. Place some visible easy to reach holes or pads for important signals, for all voltages, clocks, etc.
Use 45º angles with traces
Sharp right angle turns are always cause problems, so avoid right angels.
Pay extra attention for bypass capacitors
Spend some extra time for reviewing the bypass capacitors. To reduce noise, ripples and other unwanted AC signals, keep the track to input as direct and short as possible, also if the design is multi-layered use a direct via to relative ground plane.
Keep grounds separate
Separate the ground of power circuits from digital circuits and sensitive analog circuits, which are usually low voltage and current unlike the power part. Voltage and current spikes from digital circuits can generate noise in the analog circuits. If you tie them together in the PCB, do it in a point near the end of the supply path.
Learn the specifications of the manufacturer before routing
Not all manufacturer has the same system and tools, most have their own specifications, such as minimum trace width, spacing, number of layers, minimum via drill size.