yeah just take some time and study some maps.Especially old maps with rivers + deltas and mountains + hills on them.See how rivers flow from mountains our large plains usually in the center our close.irregular shaped bays and inlets ect...
I'm a writer, and there I find myself with the same problem. The best method I've heard is to take a piece of paper, and chop it into irregular pieces, then shuffle the pieces together. Where the pieces meet, place mountain ranges. Then decide where the sun is going to hit this planet (it may well be the axis of rotation, rather than perpendicular to it) to determine climate ranges. Then grab a basic geography book for tips as to where to place things like deserts (usually opposite a mountain range) and plains and such. Make some rivers, and place forests and other such environments around them (in the appropriate climates).
For manmade things, start at any random place (probably plains, near a river) make a city, then branch off. Divvy up the settled land into nations and vwalla. You should probably clear any forests near the human/humanlike developments, unless they're something like elves.
It's an engaging process, but it works quite well for campaigns (Dungeons and Dragons), books, and video games. The other alternative is quite simple, and in some cases more effective: make what you need and branch out from there. In this way, the world will fit the story/game. This method is easier, but often it creates worlds that feel artificial.
The first thing that looked obvious to me is that your world map lacks ice poles. That gives the feeling that what we see is just a small part of the world.
Other people pointed out that the lack of projection distortion gives this feeling too. The usual projection we use for ol' good Earth maps is cylindrical. One of the effects is that we are used to a world map twice wider than it is high. Your map is squared, this also gives an impression of it being a fragment.
I would add another oddity : presuming that your world is about the same size of ours, you shouldn't put rivers on the map. At this scale, usually, it is not worth the trouble.
If you want to keep things realistic, you should be very aware of the scale you are using. The big lake I see on your map is as big as the Black Sea. If it is, as I presume, a mountain lake, this is a highly improbable feature. Most of your rivers seem to be as long or longer than the Nile itself, maybe you would like to look into that.
A final advice on world maps : we react to our worlds map because we put a real meaning behind the lands of Africa, Russia, America, Europe, Japan. Older maps used to put symbolic pictures inside of countries to illustrate them. A Zulu warrior in Africa, a Tuareg in the Sahara, a Mandarin in China, Apaches in America. If you want people to relate to your map, there should be such clichés available for each continent. An island is less expressive than an island with a drakar drawn next to it. ("they may not be just peaceful fishers")
About cities : walk in a big city and you'll see that 80% of the town is not a very interesting place. It is an environment where stuff can happen but this is just a setting, like a forest or a mountain path. There are key points in cities : business centers, commercial hubs, railroad stations or airports, nightlife centers. For technical and human reason, it is often not desirable to make a whole city explorable. But if you wish to give an idea of its size, putting several disconnected "zones" on a map of the city can have players acknowledge of its grand size.
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