Hi, is there any specific speed or type of Micro card I should get?

I presume you have to manually transfer all apps from the tablet to the card each time I install something, or just it just get added to the overall total memory?

Thanks

You don't mention which tablet you have buy any micro SD should be fine. Depending on table, some will benefit from speed of class 10 card, others won't.

As for installing apps to SD card, there is a android utility called app2sd which can move the files for you. However on latest versions of android, you can no longer move apps to SD card without rooting the device.

I have an Asus Memo Tab 8.

So if you have a 16GB tablet with SD card facility, you can't move any apps or games to the card?!

Many apps are designed to work moved to SD, and Android versions after about 2.3 can be set to automatically move apps once installed.
Rooting the device, and partitioning the SD card, allows many more (but not all) apps to be linked into the extra partition emulating the device's main memory.

I think what c4rv meant, was that modern devices have some built-in memory (which Android refers to as SDcard0 or similar) and the device now installs apps to this instead of the card in the SD slot (referred to as external_SD or SDcard1 or similar).
Whereas older devices could only install to the main RAM without an SD card slotted in and configured.

Sorry to clarify, apps will be installed build-in storage. You can store application data on SD-Card but not the files.

TBH, this shouldn't cause an issue as most applications are pretty small. 10's of MB at most.

The real problem is RAM, when people get out of memory errors they automatically think about using an SD Card but the real problem is running out of RAM. You can check this in Settings -> Apps -> Running