I ride about 300 - 400 miles per month. The 2 most important things to make your ride great are:
1. tire pressure
2. a clean and lubed drivetrain
I have a good quality floor pump and pump my tires to 120 psi at least once per week. That's the easy part.
The chain is one of those things that you get out of it what you put into it. You should clean and lubricate it every 100 miles to minimize friction that will slow you down and cause unnecessary wear. I use ProLink chain lube. Start by wiping your chain as clean as you can get it with an old rag or strong paper towel. Next, fold a clean paper towel into fourths. Position the towel under the chain links where you will apply the lube so the lube doesn't drip onto your rim and tire. Apply the lube to each link being certain that you get enough lube on the link to penetrate all inside surfaces. Once you've lubed the entire chain, turn the crank gently for about 20 - 30 seconds. Now tighten your grip on the chain with the towel and turn the crank. This will wipe off the excess lube.
Every third or fourth time that I lube, I perform a major service on the chain that renders it in pristine condition. This is especially critical before a long ride and will take 2 hours of your time and will need to be done outdoors. I remove the chain and soak it in orange solvent or gas for about 15 - 30 minutes to remove all the grunge, grit, and grime. I have a Sram quick link ($10) in my chain that allows me to remove the chain with just a flick of my wrist. I use a plastic container with a lid so I can swish the gas and get all the gunk off. Remove the chain from the solvent and wipe with a paper towel or rag. Be sure to get it really dry, especially the inside of the links. You may need to lay it on some newspaper for an hour or so after you wipe it to be sure that all the gas / solvent has evaporated. Be sure to remove any grease that you can see.
While your chain is drying, remove the back wheel from your bike. You now want to clean any grease, dirt, and grime from the rear derailleur. If you keep up on this, a rag will do the job; if not, use some orange solvent (sold at bike stores). You want to be sure to meticulously clean the derailleur pulleys. Notice all the grease that cakes on them? Make all those parts as clean as you can get them.
Next, clean the front chain rings and the rear cassette. You want to remove all grunge, grease, and grime. I use an old rag and get in between the chain rings on the rear cassette. It's tedious, but well worth it for the performance.
Your chain will look brand new. Now lube it as described above. You will not believe the difference a clean and lubed chain makes. I replace my chain with a Shiman Dura Ace chain ($55) every 1,000 miles. The chain will stretch and wear your chainrings and rear cassette if allowed to wear excessively.
Bike shops charge for tune ups and replace cables and adjust them and the brakes. They check how the gears change to be sure that they are in adjustment. Trust me, no bike shop will clean your chain, chainrings, rear cassette, and deraillerus as I've described above. The tune up won't make you go faster; fanatically cleaning and properly lubricating the chain will optimize your performance by minimizing the friction. You will feel your bike glide down the road. Enjoy your ride!