People have learnt how to do these differing parts by going on a number of courses and having years of experience whilst learning off more senior members of their team/company
Servers-i would choose rack mounted servers, amount of RAM and CPU is hard to tell as I don't know what your website is hosting,what people will be doing on the site and the amount of data people will be pulling from it
Switches - Two is always preferable as you want redundancy
SAN - I would say iSCSI BUT it will depend on what kind of response you want from the storage, if your site needs to give live updated data in a large volume to the second then you will need faster SAN response times and therefore FC might be a better option
FC Switches - these will need to be both IF you decide on FC storage
VMware licencing - Depends on what features you want as Enterprise could be abtter fit if you don't require the added features that ENT+ has like distributed switches for example
Backup - Don't use tape! Do data backup from companies like commvault or Veeam to name just two
SAN Vendor- depends on if you choose FC or iSCSI and the kinds of IO you are palnning on, a reseller of these products could help you with this
Server Vendor - Depends what size of servers you need which is as satated earlier dependant on your workloads
Seperate DB and webserver is straight forward - Depends on what your Website is hosted on but I'll assume IIS so setup an IIS websserver and a seperate VM for the SQL server
you say 1-2 webservers - I'll assume you are planning to do an NLB cluster on these for redundancy and to balance the throughput
Clustering for DB - This isn't the easiest thing to do in VMware but there are kb articles detailing step by step how to create this and it also depends of you are looking to do physical to virtual clustering, clustering in a box (both on one ESXi host) or clustering across a box. How to create these are covered in VMware kb articles and on the microsoft website
other misc servers - this is like asking me to design for anything which is obviously impossible for me to comment on as would need to know size, workloads, type,IO,connectivity
Number of servers - at least three as HA needs a failover server and so if you state admission control needs to reserve one host in case of failure you are losing one host so doing three will allow all three to do a certaing amount of work
2 SANS - Not unless you are planning site recovery in case of a catastrophic site failure. one should be plenty and will have built in redundancy via RAID,multiple PSU etc
Disclaimer
This is my two cents worth and I bet a number of people will disagree and it really does depend on what you are hosting on that website
As for responses on this, as Niels said we don't work for VMware and aren't paid to answer questions on here. We do it becasue we use the software daily and are sharing out knowledge (refer back to your question on how people learn how to do this stuff)
Gregg