Hello.
A newbie here.
By default I have all the ports bridged, including the one which I am using as WAN.
Should it be part of the bridge, as the rest is under DHCP server NAT-ed ?
If you want to use as switch, yes.
If its for use as a router, no… but then need more info what you want to achieve…
But you will also need to adapt IP settings, interface list etc…
If the device is being used as a switch there is no WAN port, just a trunk port coming from one source and its part of the bridge yes!
Just to clarify the confusing response that is not really germane because the OP noted the LAN has DHCP services etc…
Whereas a switch does not usually provide any such thing. 
the WANIP in Mikortik is usually handled by the IP DCHP Client settings
or if PPPOE under the PPPOE settings.
The WAN is not part of the bridge normally and is identified as being the WAN interface
/interface list
list=WAN default
list=LAN default
/interface list members
add interface=ether1 list=WAN
add interface=pppoe1-out list=WAN
add interface=bridge list=LAN
Totally right:
But it’s fair question. I’d say if you have one WAN connection with a single IP, and one (or limited number) of LAN(s), the WAN should NOT be in the bridge. You can use QuickSet, and be in a pretty good place for basic networking. The bridge would be for the LAN, or other client VLANs. ROS does routing for internet/WAN, and switching for LANs/VLANs.
But if that WAN line is subnet, like /29 (5 public IPs) or bigger. Then the WAN can be trunked to another router/switch/security appliance, if needed. Here “VLAN Filtering” and treating the WAN like another (but special) VLAN isn’t a bad approach. If you do this, just make sure the VLAN interface used for the "WAN"is listed in the “Interface Lists” as WAN so the default firewall stuff just work.
The various approaches are laid out very well here:
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
Required reading if you need to go beyond using QuickSet to set up the router/switch (e.g. you have >1 WANs and/or >1 LANs).
Disagree, unless this is a wifi device where the choice of WISP vs AP vs something else has to be made.
If this is a router scenario, do not use quickset.
If this is a switch (no wifi) scenario no need to use quickset after selecting bridge (and even that is not really required)
Since I am newbie on this forum as well - I were expecting to receive some sort of a notification for a post replies, but well.. there is none.
Thank You very much to everyone that made the things clear. 
I decided to remove the WAN from the Bridge.
It’s a normal router situation.
Btw - what is the issue with quickset ? Since I used it, and now i am worried.