A tip from the Old Welder.

When making a butt weld some books told you to "V out both sides and weld it up with multiple passes.  

Great, But why waste the time?

Gap slightly wider than the electrode, then tack on a run-off strip to support the puddle.  
Use low hydrogen electrodes only, weld complete joint in one pass, keep joint hot, slag will boil out sides.  
Knock off extra strip and finish with a capper pass - Frank Tabor.