The pins HEATER_0_PIN=13 and HEATER_BED_PIN=12 are defined in pins_SANGUINOLOLU_11.h if you are using Marlin 1.0.2 or newer (or in pins.h for older versions, search for MOTHERBOARD == 62). There you can switch the pin numbers.
If you have a voltmeter, you can also first check the voltage on HEATER_0_PIN to see if it goes high when switching on the hotend. Logical pins 12 and 13 are on physical pins 18 and 19 of the 40-pin 644P/1284P microcontroller chip (see here). This way you can check if the signal at the MOSFET gate is okay (-> MOSFET problem) or not (-> microcontroller or configuration problem).
If you have a voltmeter, you can also first check the voltage on HEATER_0_PIN to see if it goes high when switching on the hotend. Logical pins 12 and 13 are on physical pins 18 and 19 of the 40-pin 644P/1284P microcontroller chip (see here). This way you can check if the signal at the MOSFET gate is okay (-> MOSFET problem) or not (-> microcontroller or configuration problem).