Best day trip from Edinburgh?

I would go to Stirling. The castle is spectacular. The walk up from the train station is good. Just seeing the geography will help you understand Scottish history. Also, you can visit Argyle's Lodgings if you want to. You can take a public bus to Bannockburn. I don't know if you can get to the Wallace Monument by public transit. It's a good view at the top of a Victorian Tower.

Pam

i agree stirling is a great option. st andrews is also a good daytrip from edinburgh. castle, abbey, golf courses, beach. and if you want to travel south there are some nice abbeys, etc.

You might want to take a look at the Heart of Scotland tours. They have a variety of day trip destinations. My daughters and I took their Loch Ness and Legands tour a couple of years ago. It was the most fun that we had during our 3 weeks in Europe. Here is their web site: http://www.heartofscotlandtours.co.uk/
Hope you enjoy your visit to Scotland!

I enjoyed a Heart of Scotland day tour (don't know if they still do it, went all the way to Hadrian's Wall), also a Rabbie's day tour (much closer, to St. Andrews).

A day tour I made for myself was to take a bus to the National Museum of Flight, http://www.nms.ac.uk/our_museums/museum_of_flight.aspx

I studied bus schedules to get the right ones, though do show up at the stop beforehand, 10 min or so. I was almost on time but the bus was leaving as I arrived. Fortunately I was able to get the next one with just a detour to North Berwick for a connection, and it turned out to be a nice detour with views along the coast.

Another day tour I made for myself was take the train to Carlisle. It was a day with a service at the Cathedral; then I thoroughly enjoyed the Tullie House, http://www.tulliehouse.co.uk/. Carlisle also has a castle to visit.

Cheers.