I generally tend to avoid organised trips and tours as you normally end up paying through the roof for them. Instead, I opt for the (you guessed it) free ones – well, nearly free (you’ll usually have an opportunity at the end of the tour to give a donation if you feel the guide is deserving).
Many towns and cities around the world have free walking tours taking place a few times a week if not every day and a quick Google search will bring up any nearby excursions. They’re usually run by friendly, knowledgeable locals who guide you through the streets of their hometown, pointing out interesting landmarks along the way. Because your guide is from the area (and working for tips) you can expect them to be helpful, welcoming and educated on the local history and culture.
I’ve had some wonderful experiences on these free walking tours while abroad. Just be aware of the weather though – I nearly lost my toes in the freezing cold snow on a jaunt around Ljubljana last winter.