The planet Mercury can be very tricky to observe. It’s close proximity to the sun means we generally only have brief opportunities to observe it low on the horizon either before or after sunset.
Right now Mercury is approaching maximum eastern elongation (on March 15th to be precise) meaning the planet is up for longer after the sun sets. The window is still pretty brief with only about 45 mins of useful time to work with after sunset.
Your best chance is to pick a clear evening and head out somewhere with a good unobstructed view to the West. You don’t need dark skies as the Sun will still be producing a lot of light between 6 and 8pm.
At the moment, and at Highland latitudes, the action starts about 6.30pm just after the Sun sets. Wait a while then scan the western horizon and you should see Venus first, which will appear brighter. Use this as a guide for finding Mercury which will sit slightly above it over the next few days.
The longer you wait after the sunset the easier Mercury will be to see due to darkening skies but also harder due to it moving lower and lower towards the horizon, adding more atmospheric distortion to your views.
If you do see it take a note of its crescent phase. We almost always see Mercury as a crescent because it would be too close to the sun to see it in a full or new aspect. One exception to this is during a solar transit when Mercury crosses directly across the disc of the sun. The next opportunity to witness this will be 11th November 2019, which gives you plenty of time to prepare a solar filter for safe observing of the solar disc. Happy planet hunting meanwhile.