winkey + space : Switches between language input methods.
alt-~ (tilde) : Cycles between Hiragana/Katakana (Kana) and English.
alt-caps_lock : Switches to Katakana.
ctrl-caps_lock : Switches to Hiragana.
space : You can convert Romaji into Kana or Kanji just using SPACE and ENTER.
up/down : Alternatively (or sometimes after SPACE) you can use the up/down keys to select other Kana or Kanji options.
enter : Confirm selection.
You can customize the keyboard shortcuts for this input method by right-clicking the "中" or "英" character on the taskbar then going to "Settings".
Default keyboard shortcuts:
ctrl + space : Chinese/English mode switch.
shift : Chinese/English mode switch (this is default but it is customizable).
ctrl + shift + f : Simplified/Traditional Chinese Input Switch.