That does depend on the firewall you use. Using the "pf" firewall you can have nice clean rules which covers both.

Simple example:

    tcp_inbound = "{ ssh, domain, http, https }"
    tcp_outbound = "{ domain, http, https, imaps, smtps }"

    udp_services = "{ domain, ntp }"

    block all
    pass proto udp to any port $udp_services keep state
    pass out proto tcp to any port $tcp_outbound keep state
    pass in proto tcp to any port $tcp_inbound keep state