Stored Procedure With Optional/dynamic Where Clause

If I do this with a function and multiple inline sql statements, I could probably do it much easier, but here at work, sprocs are required, and I can't seem to stretch my knowledge and Google searches far enough to find the answer. Plus, I don't really think that creating 4 separate sProcs is the most efficient way of doing this

I need to select and return 8 columns from a table, but the problem is I need to feed the sProc parameters in such a way, that I can use different criteria in the Where Clause.

for instance, I need to combine these 4 select statements into one:
1. Select (fields) from (table) Where TechID=@TechID and Status=@Status)
2. Select (fields) from (table) Where TechID=@TechID
3. Select (fields) from (table) Where OrdNum=@OrdNum
3. Select (fields) from (table) Where CustNum=@CustNum

In all instances, the fields and the table are the same - how can I combine all these possible Where clauses (if/then - Select Case?) so that it's only one Stored Procedure?

(or, is this even possible?)