"To guide" can have different meanings and the appropriate Tagalog word depends on the context.
In a moral or ethical sense, patnubay would be appropriate.
Diyos ang kaniyang patnubay sa buhay (God is his guide in life).
In the sense of serving as a guide or model, huwaran would be applicable.
Siya ay ang huwaran ng mabuting ama (He is the model / guide of a good father).
In the context of precepts to follow, you could use gabay.
Ayon sa mga gabay tungo sa mabuting kalusugan, dapat nating panatilihing malinis ang ating kapaligiran, kumain ng mga sariwang gulay at mag-ehersisyo araw-araw (According to the guidelines for maintaining good health, we should keep our surroundings clean, eat plenty of fresh vegetables and exercise daily).
When speaking of a teacher or instructor who gives specific steps to follow, you could use tagapagturo.
Siya ang tagapagturo ng wastong pagpapatakbo ng makinang iyan (He is the guide / teacher to the proper operation of that machine).
There are many other applicable words, according to context. Also, the Tagalog words I mentioned can be applied to alternate contexts. For instance, either huwaran or tagapaturo can be easily applied to a moral or ethical context.