Counters are very common experiments on digital electronics subjects.
Here's a simple up/down counter that uses 74190.
This circuit is easy to implement and here are some of its features:
Presettable - having this capability, it is easy to use for down timers with initial value like 24second shot clock.
Parallel output(BCD) - its bcd output can be easily interface to a bcd-to-sevensegment decoders.
Ripple clock output - you can cascade many 74190 to form 2digit, 4digit and Xdigit counters.
Single input pin for up/down - in case that the requirement is to control the count in a single pin, this 74190 is very applicable.
Please note that you need a switch debouncer on the switch so that you can have a clean count..
Reference for switch debouncer.http://www.circuitlab.org/2008/12/switch-debounce-circuit.html