A few years ago I bought an investment property. At that time my credit was pulled by three potential mortgage lenders. This lowered my credit score. Immediately after the loan closed (actually on the same day the title transferred) I applied for three different credit cards, and each one was granted with the available new balance totaling about $60,000.
Getting the credit cards caused my FICO score to drop significantly. Since I had just completed the loan for the investment property and knew I wouldn't need to have my credit pulled for another 6-12 months, I was ok with this.
On each of the cards I put one small subscription to something I already had (for example, I use one of them for my NetFlix subscription, which was around $12 at the time and is now a few dollars more). I set them all up for monthly full-balance autopay from my checking account. The purpose of the small recurring transaction is to make sure the credit card companies don't close the accounts for inactivity.
I have never used these cards for any other credit transactions. To me, they're not "real" credit cards. Their sole purpose is to increase my overall available credit amount so my month-to-month credit reporting shows a much lower credit utilization even though my normal credit spending hasn't changed. I will never use these cards for any transactions beyond the one monthly recurring subscription. The cards are physically in a safe - I don't carry them in my wallet (out of sight, out of mind).
After six months or so my FICO score was about 70 points higher (well into 800) than it was prior to getting the cards, with no real change to my spending habits.
For me, I think it was a great thing to do, but I never carry an interest-accruing credit balance. I use credit cards (the ones with the highest cash-back percentages) for all my purchases, but I always spend less than my available cash-on-hand, and I always pay them off in full within 30 days.
If you have the discipline to NOT use credit cards to spend money you don't own, then they're a great way to increase your credit score. If you aren't good at managing your money, then learn how to use a small balance credit card correctly (i.e. treat it like a debit card and pay it off in full every month before your statement date) before trying this. Also, do make sure when you get the cards you aren't planning to get any loans within about six months as you'll take a credit hit for a while.
Finally, another interesting side effect of doing this was that the credit cards I do use all auto-raised (without me asking) my available balances! They periodically pull my credit score so it was as if they saw I had more credit available elsewhere so they raised my limits to try to get me to use their cards instead. Now my available credit on my credit cards totals around $125,000. Again, my spending habits haven't changed (i.e. I don't use the extra available credit) so my effective utilization is now much less (in my case always less than ~7% per month).