Plagiarizing myself from a previous thread, here's how i like to set an initial tempo:
- Disable Stop at Project End in Track View Options if it isn't already so you can run the transport in an empty project.
- Start playback with no click sounding, count off a couple-few measures in your head, and stop the transport on the next downbeat.
- Shift+M to open Set Measure/Beat At Now, and enter that measure and beat.
- SONAR will set the tempo to make the specified beat fall on the absolute Now time where you stopped the transport.
This gives very accurate results in a new project with low latency where the transport start/stop is almost instantaneous. Note that SONAR will also insert a matching tempo at the beat you set. It won't matter unless you go changing tempos later, but you can delete it if necessary.
This works especially well when setting a tempo for someone else. You can just ask them to count or beat a tempo and start/stop the transport on their count.