Blade: Carbide tipped, wide-ish kerf rip blade is preferred. Choose a blade with fewer teeth, for ripping the tooth count is not quite as critical as crosscutting or finishing cuts, the fewer teeth create less total friction, and the more open gutters between the teeth are better equipped to deal with the long stringy chips created by ripping, especially softwoods. This creates less drag as well. Forrest and Freud make great blades. Set the blade to the highest setting when ripping. This minimizes the tooth contact area and presents the least load to the motor. Keep the blade clean and free from sap and pitch. Sap is a big problem when cutting dimensional softwoods. Waxing the blade is a good idea.
Alignment: The fence must be parallel to the blade, and the blade must be aligned to the table. Adjusting the trunnions makes the blade move in relation to the table, the blade must be absolutely parallel to the miter gauge slots in the table.If you don't have an alignment jig, clamp a fixture to the miter gauge so the dial indicator touches the side of the blade. A stick screwed or clamped to the miter gauge can hold a dial indicator adequately. Slide the miter gauge/indicator combo back and forth with the blade set at its highest. There should be no change in the distance. Adjust the trunnions until there is no skew. Now adjust the rip fence until it's parallel to the blade, use a fine ruler to measure the difference between the front and back of the blade in relation to the fence. The screws that hold the fence to the clamping mechanism are generally the adjustment points. With the fence tight, loosen the screws then move the far end of the fence in the direction needed to achieve parallel. Waxing the fence sides as well as the table helps too.
Powertrain: Make sure you have a solid electrical supply to the saw. No extension cords, no 15 amp outlets situated a thousand feet from the panel. Check the belt and pulley for wear, and if the belt is old and stiff, replace it, preferably with one of the Fenner link-belt systems. Clean all the sawdust from all moving parts.
Lumber: Some 2by dimensional lumber is just plain ****. When ripping, the uneven drying makes the kerf close up on your blade, couple that with softwood's sap, you'll create drag. Make sure the splitter (if you have one) is doing its job.