Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

          Qǐng gàosù Xiǎo Lǐ lái wǒ nà'ér .
False: 请告诉小李来我那儿。
          Qǐng gàosù Xiǎo Lǐ lái wǒ zhè‘ér .
True: 请告诉小李来我这儿。

远指和近指的混淆。“小李”的行为动作“来”是朝着说话人(“我”)进行的,距离说话人很近。应当用“这儿”。
The error lies in the confusion of two words of close and distant reference respectively. 那儿 refers to a location further away from the speaker while 这儿 refers to somewhere around the speaker. The action 来 which is towards the speaker(我)brings 小李 close to 我. Thus 这儿 is the right word.