When taking a taxi...
When taking a taxi in Bulgaria, make sure to check the price list in the back window before getting in the car.
Most of the cabs on the streets of Sofia (and Plovdiv for that matter) start off at about 0.59 BGN a kilometer, and that's just fine. For Jodie, taking a taxi to work should cost about 3 Leva. Prices of taxis are quite cheap, actually. When we took one to the airport (30 minutes' drive), admittedly at an hour when there was no traffic, the bill came to about 12 Leva.
What you have to be careful of, is not getting into a private taxi, where the rate is more than 2 Leva a kilometer. You have no choice but to pay the higher bill, because the price of 2.50 Leva/kilometer was posted in the back window. It happens to everyone. Just the other night, I was in a hurry to catch a taxi into the center of the city and didn't check the window. For a short drive, I paid 16 Leva.
Even if you get into one of the cheaper taxis, you could be taken for a ride. When we were in Plovdiv, we had a very nice driver. Although he didn't speak a word of English, he kept going on about how Israel was a good country. Apparently he was trying to divert our attention from his "fixed" meter. It started out at 0.59, but was jumping up at an amazing rate. We ended up paying 13 Leva for a ride which should have cost us only 3 Leva.
And finally, you're not supposed to tip taxi drivers. Just pay them the amount registered on the meter. But, don't expect them to have, or make change. If the price is 3.70 Leva, and you give them 4, they'll pocket the difference.