How I planned a 12 day Europe trip in budget

International trips are really exciting but drains pocket at the same time, especially to destinations like Europe and US. But if you plan your trip properly and ahead of time, you can save a lot of money and travel to your dream destinations in budget.
The four major things that constitute 80% of our trip budget are flights, accommodation, food and internal transfers.
Regular travelers save a lot of money in these 4 things to make their trip budget friendly.

Sharing my own experience to plan a budget international trip.

FLIGHTS:
1) Start your travel planning 2-3 months before your travel date. Bookings flights ahead of time saves a lot of money.
2) Prefer budget airlines with cheaper rates rather than luxury airlines.
3) Be flexible with dates as flights rates may vary a lot between different dates especially between weekends and weekdays.
4) Use google flights to compare flight rates for different dates and different airlines.
5) Use airlines membership to earn points and use it for booking flights.

ACCOMODATION:
1) Prefer airbnb over hotels. Airbnb's are much cheaper and comfortable in most European countries and in US.
2) Most Airbnb's offer breakfast and good views, prefer those.
3) If you are choosing hotel, choose budget hotels like ibis budget etc with decent facilities.
4) Airbnb's with owners staying in the same house are more preferable in terms of security, hospitality and guidance.
5) Couchsurfing is another good option to stay free of cost.

FOOD:
1) Carry your own packed foods. Most Airbnb's have kitchen or at least microwave where you can heat your ready to eat stuff.
2) Carry your water bottles during sightseeing as water can be expensive in US and most European countries. Most European countries have drinkable tap water.
3) Carry your own snacks like biscuits, protein bars etc to keep you energetic during travel.
4) Prefer hotels and bnbs which include breakfast. Have a heavy breakfast to keep you full for half a day.

INTERNAL TRANSFERS:
1) Check for travel passes like train pass, bus pass etc which can be much cheaper than individual travel tickets.
2) Choose your hotels and Airbnbs either near airport or in the main city to avoid cab costs.
3) Prefer walking for nearby locations.
4) Use public transport as much as possible. It us much cheaper than private cabs.
5) There are places which offer you cycles at minimum cost or no cost. Read travel blogs and websites for such information.

The rest 20% includes miscellaneous items like entry tickets, shopping, souvenirs, snacks etc.
You can plan these miscellaneous items as per your budget.