...

Until this section is more complete, use

MDBG or yellowbridge

to look up characters and a textbook such as Reading & writing Chinese: simplified character edition by William McNaughton and Li Ying.

...

In this course's Conversation vocabularies and Dictionary, Traditional Characters are written in brackets, except for easily recognisable Simplified elements such as: 讠(言)，贝(貝)，见(見)，金(金)，马(馬)，鸟(鳥)，门(門) and 鱼(魚).

Frequently one Simplified character results from two or more Traditional characters. Note:

• Traditional characters make this difference depending on whether 'you' is male or female: 你 (male), 妳 (female), both nǐ.
• 侄子 zhízi 'nephew' and 姪女 zhínǚ 'niece' are simplified as: 侄子 and 侄女.

Sometimes usage is just different:

• 老闆 lǎobǎn 'boss' is 老板.
• 藉口 jièkǒu 'excuse' is 借口.

Do you just have to memorise them?

...