Katakana represents the same phonetic sounds as hiragana except all the symbols are different.
In modern Japanese, katakana is most often used for transcription of words from foreign languages (other than words historically imported from Chinese).
Due to the straight lines and relatively few strokes, there are many characters in Katakana that look very similar.
A simplified chart without stroke order is shown below:
Here are a few samples of foreign words using katakana:
アメリカ –> America
ロシア –> Russia
バス –> Bus
バイク –> Motorcycle
フライドポテト –> French Fries (technically “fried potatoes”)
Practice writing the katakana characters to help commit them to memory. You can do this on a blank sheet of paper or here are some easy practice sheets you can print out below. Make sure you practice the proper stroke order. It will be helpful to get in the practice before moving on to the more complex Kanji.
Practice Sheets: http://japanese-lesson.com/characters/katakana/katakana_writing.html