Hello,
The first sign would be missed periods in a normally woman with regular cycles.Is she misses it,then then first thing to do is take a test.The other symtoms like nausea,vomiting,dizziness,weight gain, etc start after 2 mths.So if there is a missed periiod,take a test immeidately.

Dear imran
welcome to healthcaremagic
The signs of pregnancy are as follow
Missed period      
Unusual or abnormal period      
Just "feeling" pregnant      
Changes in libido      
Soreness of the Breasts      
Enlargement of the Breasts      
Frequent Urination      
Strange Cravings
Fatigue      
Montgomery's Tubercules      
Skin Changes     
Stretch Marks      
Enlarging Uterus      
Movement      Possible
Colostrum from Breasts
Enlarged Abdomen      
Change in uterine shape      
Braxton Hicks Contractions      
Palpation of the Baby      
Positive Pregnancy Test      
Fetal Heart Tones      
Ultrasound Detection      
X-ray Detection

Thanks