Using what you already have...

Seems too obvious??  You can add a whole lot of new detail to your family history research simply by rereading those certificates that you bought ages ago, or that newspaper cutting that you clipped and tucked away for safe keeping. Witnesses on birth certificates were often relatives, especially in early times. Witnesses on marriage certificates were and quite often still are relatives. Read those obituaries. See if the coffin-bearers or pall carriers are relatives. You may not have been able to place them at the time but a tiny scrap of information now may get the light bulb going and open up a whole new avenue of research. Best of all because you have already bought the certificate ages ago or noted the record, this kind of research will not cost you anything but time. So dig out those old certificates, newspaper cuttings or all those old notebooks you have tucked away and go through them! You will be glad you did.