Question: How to create custom markers and when mouseover on marker I need a tooltip. Can any one suggest to me how to do these type of markers?

I need markers like in the below image:

![enter image description here](https://i.stack.imgur.com/jYP6J.png)

Answer: 
You can create custom markers with code similar to the following:

```
var iconBase = 'https://maps.google.com/mapfiles/kml/shapes/';
var marker = new google.maps.Marker({
    position: myLatLng,
    map: map,
    icon: iconBase + 'schools_maps.png'
});

```

See the [Custom Marker Documentation](https://developers.google.com/maps/tutorials/customizing/custom-markers) for more details.

As for the 'tooltips', check out the [InfoWindow Documentation](https://developers.google.com/maps/documentation/javascript/infowindows).

And here is a [jsfiddle that demonstrates a custom marker with an infowindow](http://jsfiddle.net/fn55p/5/).
Your screenshot seems to display markers with labels (The orange small box with the two red boxes). Just go to the [google-maps-utility-library-v3 website](https://code.google.com/p/google-maps-utility-library-v3/wiki/Libraries) and you will see in action markers with labels like in [this demo](https://google-maps-utility-library-v3.googlecode.com/svn/tags/markerwithlabel/1.1.8/examples/basic.html). The API docs are [there](https://google-maps-utility-library-v3.googlecode.com/svn/tags/markerwithlabel/1.1.8/docs/examples.html).

For the only "big box" with all infos, to custom, you can use instead of InfoWindow the InfoBox component with the [link to API and samples](https://google-maps-utility-library-v3.googlecode.com/svn/trunk/infobox/docs/examples.html). InfoBox component is not native, it's a component extending Google Maps v3.