I find chisel shaped round tips to work really well and give versatility when working. Curved tips too because solder doesn't like to gather on the point of sharp tips. You'll also need an iron that can hold temp very well as the smaller the tip, the easier it will transfer its heat, leaving you with a cold tip welded to hard solder while waiting for the iron to heat up again. In a worst case scenario, your iron won't be able to heat the tip quick enough and the board will leach the heat out, resulting in burned components or a torn trace.