Placing the components and routing the signals as much art as science. It is best to finish the board and then go away for a day or two. When you come back you can often see ways to improve it.
It helps to run through a tutorial or two.
Observations:
DRC (Design Rule Check) is used to check you layout for problems. It checks for clearance between traces and pads. The default is 8 mils. It is also where you can change the restring value which determines how large you pads will be. The default is 25%. I often use 35% which provides larger pads. Some connectors will not allow you to up the restring value
There is no good reason to use 8 mil clearance if your board will allow 10 or more. I like to route the board at 8 and change it to 10 whien I am finished. DRC will show me where there are clearance problems. Where possible I fix them to achieve 10 mil clearance. The ones I can not I leave alone. Then I set the clearance back to 8 and run DRC again to make the unfixable errors go away. I now have a board with 10 mil clearance execpt in a few places where it is not possible.
The default trace width is .016. Execpt for lines that carry current (power and gnd) I like to use .012 or .010 inch traces.
Neatness counts.