In general tickets are easy to get unless you want something specific and try to do it last minute. Expect to spend anywhere from $35 to $250 depending on what you want. Weekend games will run you about $20-50 more per seat on average compared to a weekday game.

If you're not picky you can often save money buying resale close to the game starting, but based on how you buy them and how expensive they are you might get raped in fees to the point it becomes more expensive. The best deal I've found was on the gametime.co app where I got row 1 in section 228 for the Kings game for $80 total (including taxes and fees) - that seat in a worse section was $95+ retail.

If you buy retail the more popular games will fill up quickly and you wont have very many options. I had 110 row 17 for the last game and wanted to swap out for a pair of tickets so I could bring my brother: there were almost zero paired seats left the week of the game but there were plenty on resale. I paid $69 for that seat which is one of my favorites (row 17 is one above "club level" so significantly cheaper than row 16).

I also paid around $215/each retail for row 1 seats against the oilers section 109 just a few feet to the side of the goal. Those were awesome, and the game was perfect (all 4 goals were scored in that goal and we won in the shootout with that beautiful donskoi shot). I usually spend less than half that amount but it was a special occasion, I took my dad and brother as Christmas gifts.

Start here to see what's generally open and get a feel for the prices: http://sharks.nhl.com/club/page.htm?id=83071

Then move on to the other sites and compare what you find.