Every Project Manager will have his/her specific area of expertise but most would encourage new PMs to work on becoming effective in these key areas:
1. Open Communication
2. Advocate Job Site Safety
3. Schedules and Learning the Software
4. Rapport with Construction Team
5. Paperwork- Don’t Slow the Flow
Here’s a link to an industry blog that elaborates on the points above in addition to a few others more specific to contractors.