Hey there, I can help you with the information you need for around Istanbul but I didn't travel to other cities.
Visa:
For the visa, you can simply apply by yourself, I did not visit any consultant. You'd require a notorized letter of invitation from Turkey if you do not have the supporting documents such as employment detail, tax filing data, etc. It could be sent by anyone, friend or family who is in Turkey, which will eliminate the chances of your visa being rejected. Remember, you can apply without the letter of invitation as well but you would wanna make a strong case by having all your personal documents.
Reservation Proof:
- Book a flight to Istanbul using Turkish Airline website then print the ticket, you can cancel it right after printing or it will be automatically cancelled if you wont pay.
- Book any hotel with free cancellation on Booking.com and print it as well, then you can cancel it right away, it wont charge you anything.
Istanbul:
If you do wish to stay in Istanbul for a day (Which I would HIGHLY recommend that you do!) choose Sanat Pera Hotel (Avoid Santa Pera, which has a similar name) near Istikal Street. Istanbul is basically what Turkey is all about so please don't miss out on it, it has a lot to explore and offer and every street in Istanbul would lead you to something new and awesome.
Deparature:
Before you depart from Karachi airport, strictly keep a copy of every document with you, reservation, ticket and everything extra copies. If you're travelling to Turkey for the first time and has never travelled to Europe before, the FIA would want to make sure that they waste your time in asking a lot of questions and ask for a lot of proof that you will return. Specially if you're a lone traveller, they will be extra hard on first-time travellers.
- Once again, keep extra photocopies of your documents.
- If you have any old passports, keep them with you.
Landing:
When you land in Istanbul, do not take their taxi service at the airport, they will rip you off. Get out of the airport, hire a taxi and call your friend, tell her to talk to the taxi driver and do not pay anything besides the meter. Make sure whenever you travel, pay by the meter and not a single extra lira. Turkish people are super awesome but they are very famous for exploiting foreigners.
Things to do in Turkey:
- Please as I mentioned above, spend some time in Istanbul. Try the Baklik Ekmek (Fish Sandwich) in Eminonu, right beside the sandwich restaurants there is blue mosque, visit it.
- Visit Basilica Cistern in Istanbul.
- Eat the famous Iskender Kebab in Istanbul.
- Don't dare forget to try Turkish Delights.
- Try Mussels if you're into Sushi.
There is such a long list of what you can do in Turkey, specially Istanbul but those are some must-try things.
Things NOT to do in Turkey:
- What @sashah666 said is ABSOLUTELY correct. This is a very famous scam, happened to me on Istikal Street, I was going to buy food and two guys asked if I have a lighter, I politely declined then they asked where I'm from so I said Pakistan. He started talking about Lahore and said I have a friend from Lahore, etc. Then they said they are going to see the famous belly dance and would like me to go with them, I politely declined and entered a restaurant to buy the food. Once I had my food, they were still waiting outside, they walked with me until I had reached my hotel and then I politely said I'm not interested. Be on guard about this, very important.
- There is a another common scam of shoe polisher, a old person would run into you and his brush will fall off his hand, you'll obviously try to help him and when you do, he will insist that he would like to polish your shoes and make it look like he is doing it for free, although once he is done, he will start asking you for money which trust me you will have to pay. That did not happen to me but that is very common.
- Don't pay for the things you buy right away, always negotiate until there is a price list.
- Never order food without checking the price list.
- Never pay or decide a price while travelling in taxi, always go with the meter.
- Never offer anything to girls trying to be friendly in posh neighbourhoods, they will scam you big time.
I'm not sure if it is a great time to travel to Turkey due to the recent coup attempt, but if you must go, be extra cautious since there is a emergency situation for three months which allows the goverment to mould their laws any way they want, so be careful. And please feel free to ask anything you would like to know, cheers.