This article has no intention to be comprehensive and it is based on preferences which may not be yours. 

1 - If you arrive in Berlin by air make sure you opt to arrive through Tegel airport. If you do not have the option and have to arrive via Schoenfeld airport please be aware of the following:

a) The airport is very small better fitted for a country town than for a major capital such as Berlin. The airport is quite far from the city center (Mitte District) and a taxi ride will set you at around 35.00 Euros (plus tip) which is not expensive but still a good rate when compared to similar fares in other capitals of Europe. The best way to arrive in town is by taking the train from Schoenfeld train station. To do that please make your way out of the airport towards the taxi stand. To your left you shall see a one sided roofed passageway stretching from the airport to the train station, otherwise follow those who look to you like locals since they most definitely will take the train from Schoenfeld train station.

b) You can purchase your train ticket at the ticket counter in the train station which shall cost you around 3,50 Euros one way (adult fare) leaving you in the center of Berlin at any station before or after Alexanderplatz depending on your hotel location.

c) The train ride lasts about 20 minutes to 30 minutes and you shall be in town in no time.

2 - When to go to Berlin. If you want to enjoy Berlin at its full potential try to schedule your visit between May and October. Otherwise you may find yourself in bitterly cold weather, rain or even worst, snow.

3 - What you should know before arriving. Although English and other foreign languages can be easily understood, you better brush up on your German and learn how to speak the basic words. In more than 75% of the places I did go German was the only spoken language with barely anyone understanding more than the basic English words. Most of the signs are also written in German so you better have a basic understanding of the language. Shops are closed on Sundays, inclusive supermarkets and drugstores. You might find some souvenir shops and drugstores/pharmacies open in the main tourist routes such as the Brandenbourg Gate, but that is all. Coffee shops and restaurants are however open 7 days a week. During the week days including Saturdays shops are open normally from 09H00am to 08h00pm depending on the area they are located and type of clients they serve. Kaufhof and KaDeVe the big Berlin department stores usually are open until 09Pm in the evening or 10Pm (not sure). Berlin when compared to other European capitals is quite affordable. Mind you that tourist places such those in and around the Mitte and the prestigious Charlottenburg neighborhood tend to be more expensive than those around Alexanderplatz (former center of East Berlin). Don´t be convinced that it is cheaper to buy street food than eat at the many coffee shops and restaurants that dot the streets. Surprisingly street food can be as expensive as food served in those coffee shops and restaurants, exception made once more for Alexanderplatz and other non tourist neighborhoods in Berlin. The city was extensively ravaged by the II World War and it is still been rebuilt, so many attractions, specially museums are still under construction to be restored to its old splendor. Berlin has no city center or as North Americans might call it, the downtown area. It is a wide spread city made for walking. If you do not like to walk maybe you should opt for other more compact cities in Europe. You can although define the area between Alexanderplatz and the Tier Garten as the area you should most definitely visit. Alexanderplatz is the old center of East Berlin and the most popular area for the average Berliner working class easily identified by the high steel tower with a sphere on top. From there and walking towards the so called "Museum Island" you shall visit the old and totally reconstructed Jewish neighborhood north of Alexanderplatz or the Medieval District (also totally rebuilt) south of Alexanderplatz.. West of "Museum Island" is the famous Gendarmen Market and the Brandenburg Gate with Tier Garten at its feet encompassing the Reistag and Bundes buildings and the major and most expensive shopping district in Berlin around Friedrich Strasse (Street). Berliners are extremely low profile people, dressing almost in a non descript way wearing confortable clothes and shoes. Do not expect to see people dressing fashionably or using expensive label brands, although all major brands have more than one shop in Berlin. Berliners are very well behaved people and they seem to act in a most unassuming way. You will not find many people smiling or looking happy in ther facial expressions. They are very unassuming as one might say. They can be helpfull but they do not look the part. Be aware of people trying to approach you (the tourist) with a city map asking for directions, since in most cases they are trained pickpockets trying to take away without notice your money. If you happen to be asked for directions move away swiftly and tell them straight away that you are not from Berlin. The technique those pickpockets use is to overwhelm you with the map while they will work under it to clean you of easy access money/wallets in pockets and wallets. This should not deter you to visit this city since in all the major tourist cities in the world this and other methods are also used to lure unaware tourists to similar situations.

4 - What you should definitively see. Museums: The Pergamon Museum - an extraordinary museum in its artefacts and ancient art. For me the best museum in town and quite unique. Be aware of the long lines to buy tickets and avoid that by buying your entry tickets on line beforehand. Select the day and time of your visit, print the tickets with the barcode and upon arriving at the entrance proceed to the VIP entrance (not well marked but you can see it on the ground approaching the museum entrance). You will be surprise how easy it is. Get your audio-guide for free and enjoy the visit. Palaces: The Charlottenburg Palace (not in Charlottenburg neighborhood) is another place to visit. Berlin attractions are quite expensive with tickets between the 10 Euros mark and 20 Euro mark. So if you are on a budget be wise in selecting the places you would most likely wish to visit.

5 - Walking Tour: The Jewish Quarters (neighborhood) north of Alexanderplatz and Museum Island is an area composed of tightly knitted buildings with linked courtyards featuring cafes, restaurants, shops and art galeries. Gendarmen Market: Located west of Museum Island it is a very touristic place featuring a pleasant square bearing to churches, one at each side and an old Roman style concert hall in the middle. Nearby you will find (in one of the corners) an old and famous chocolate shop and in one side streets Ritter Chocolate store where you can custom made your own chocolate bar. Proceed toward Friedrisch Strasse and bear right towards the Bund and Brandenburg Gate to visit the Reischtag.

6 - Open air places to visit: The Tier Garten: an extensive park made of beautiful woods and open grass spots where Berliners like to sunbathe and play with family and friends. At one end of the park on the shore of a pond there is the most traditional biergarten packed with Berliners and their families and friends and  lots of tourists. The Sony Center: a modern open air complex made of state of the art buildings featuring shops, restaurants and a movie complex. KaDeVe area and square featuring a ruined cathedral and the center of West Berlin before the wall came tumbling down in 1989. Alexanderplatz and the medieval neighborhood (west of the square) identified by the Berlin Tower (steel structure with a sphere on top) and the Kaufhof Dept Store.

7 - A non-tourist thing to do: Every Thursday from 05H00pm to 10h00pm the Markethalle 9 in the Kreuzberg neighborhood. This is one of the most avant-garde and mixed Berlin neighborhood featuring a large variety of ethnic restaurants and cafes, young students and artists from around the globe. At this food market, every Thursday stalls of food and beverages from different parts of the world are on offer and the ambience is not to be missed. Very relaxed and surprisingly bustling, noisy and happy atmosphere contrasts with the city kind of bland atmosphere.

Have not tried the nightlife so cannot have a say on it, but according to what people told it is varied, bustling and with nightclubs that you do not find anywhere outside the city exception made for Amsterdam.

 Enjoy Berlin