How to design index for faster deletes I want to speed up following piece of code

delete from ssn_sdo
where       
           (art_id=@art_id and skl_id=@skl_id and @level=0 )
        or (art_id=@art_id and skl_id=@skl_id and @level=1 and tip=@tip)
        or (art_id=@art_id and skl_id=@skl_id and doc_id = @doc_id)


My server is MS SQL-Server 2005.  

art_id,skl_id and doc_id are integers, while tip is varchar(10) type of.  

I want to make an index(es) on ssn_sdo table so this delete is going to faster.
What I was considering to do is to make three indexes, each one for every case:

doc_id (ASC), art_id (ASC), skl_id (ASC)  
skl_id (ASC), art_id (ASC), tip (ASC)  
skl_id (ASC), art_id (ASC),  


Or is there better way to make one index which will include all three cases.
I am careful with indexes because I do not want to slow down inserts in this table.
Bit akward, I can't see how to comment but I wanted to ask why your condition isn't:

delete from ssn_sdo
where       
       art_id=@art_id 
       and skl_id=@skl_id
       and (@level = 0 or (@level = 1 and tip=@tip) or doc_id = @doc_id)


Not sure that helps at all, before or after you add any further indexes, but it'd interesting to see the executions plans (actual) and see if any benefit is realised.