It's a week before your trip and you don't know how to plan for spending money there... What are your options?!
You should have both cash and card options with you during your trip as a precaution (but not too much cash cus you'll get mugged).
I highly recommend carrying some local currency with you since depending on the country, you'll need to pay restaurants, taxis, tips, etc. in cash. However, make sure you have two separate stashes: 1 for day to day spending, meaning you should only keep maybe $20-50 worth of USD in youor visible wallet so people think that's the only cash you're carrying. The other stash should be a secret stash of the rest of your cash. It's more of a safety tip than anything else.
When I went to Paris, I needed to buy train tickets for my family but the machine kept declining my card. All the other places I used my card was totally fine but for some reason it wasn't working, so I ended up using my card at a service booth where a real person helped me buy my tickets. Had they not had a booth, I would have needed to withdraw some cash and pay for the tickets via cash.
I'm finding that it's getting harder and harder to exchange cash beforehand at bank. My dad went into his local bank and asked to exchange USD for Yen and they said it'd take up to 6 weeks... HA! Ain't nobody got time for that. Your other option is the post office, which can sometimes be cheaper than market rate.
Your worst (but sometimes only) option is exchanging at the airport. They always have high market rates, and sometimes a service fee depending on where you go. Nevertheless, you'll always get the short end of the stick there so avoid it if you can.
Of course you can be super prepared and exchange currency beforehand, but what if you need more cash in that country? My advice is to check which international banks your home bank is affiliated with. More often than not, your banks will have a partnership set up so that you're not charged an extra fee if you withdraw from those affiliate ATM.
I have Bank of America, so my international affiliate banks are:
Please note that they call 'ATM' something else in every city. So typing ATM in Google Maps in England probably won't work... You'd have to search for 'cashpoint.' I'd also recommend looking into maximum amounts, and any other fees that you may incur on your bank's websites.
Withdrawing cash from an affiliate ATM will not charge an extra withdrawal or foreign fee, but the cash will be exchanged at the rate that the bank charges, which in my opinion, is still worth it. For me, this has turned out to be the most convenient option when traveling.
SUPER IMPORTANT: You should ALWAYS notify your bank(s) when you're traveling so they don't mark it as fraud!!!
If you don't have an option to go to an affiliate bank, then be warned that you will incur a fee every time you withdraw. Depending on your bank and account, that amount will differ. I believe the standard is something like $5 per transaction.
For ATMs that try to get you with the 'FREE WITHDRAWAL' sign on the machine, be warned that though they may no charge you for using their machine, your bank might.
And of course, if this wasn't obvious, use your debit card when withdrawing cash. ;)
Paying With card
If you travel enough, I HIGHLY recommend getting a credit card that benefits international travel. The one benefit you probably want to look for is that they don't charge for foreign transaction fees. I don't know too much about credit cards and it's a game I'm learning myself still so I can't recommend any specific cards, so... go to CreditKarma & the Points Guy and do your own research :P
I can only speak to the one card I have, which is the Chase Sapphire Reserve and it's pretty freaking bomb.
ANYWAYS get a card that will benefit YOU, meaning, you can hear what your friends and experts say, but ultimately the decision is yours and you need to find a card that will benefit you in the ways you need your card to come through.
Some of the benefits might be: no foreign transaction fees, points towards travel, some kind of travel insurance domestic and international, an international concierge number, roadside assistance, lounge membership, or reimbursement for Global Entry.
It will make your life easier knowing they have your back (like I do, heh).