I'm no expert but it depends on what you are brewing. If doing normal grav 5 gal batches, generally you can just use a rehydrated dry packet. Or a liquid smack pack. Dry yeast never needs a starter, all the nutrients etc are built into the yeast already. For lagers, a starter is def recommended to avoid underpitching, or the use of multiple smack packs, but that is pricey.
For a starter, you just take a small quantity of DME, or any similar product, boiling for 15 mins to sterilize. Cool to room temp, add yeast, shake, and let go. 1 day or two later, boom, starter. I use a stir plate I made to add air during process which helps increase yield of growth. The process can be altered in many ways but that is the gist.
For the last lager I did, came out great. I made a starter like above, let cool in refrig for 1 day, poured off top "beer" and made another starter using that batch to make a bigger one. Repeated that in the fridge again, and made one last for about a 5x original amount of yeast. That's called making a stepped starter.
It's all very easy, sanitation is important.