Note: Not all the rules of constructing sentences are included here. This is just a basic rule to remember the Serbian word order.

You can use almost all the combinations of Word Order. Thanks to Cases!

SVO - Subject - Verb - Object - this always sounds natural

VSO - Verb - Subject - Object

OSV - Object - Subject - Verb

SOV - Subject - Object - Verb

OVS - Object - Verb - Subject

VOS - Verb - Object - Subject

Example:

I am eating watermelon.

SVO:

Ja jedem lubenicu.

 s    v        o

VSO:

Jedem ja lubenicu.

     v     s     o

OSV:

Lubenicu ja jedem.

       o      s    v

SOV:

Ja lubenicu jedem.

  s    o        v

OVS:

Lubenicu jedem ja.

       o        v    s

VOS:

Jedem lubenicu ja.

      v       o      s

There are some sentences here that sound strange but you can say it like that. Everyone will understand you and won’t misinterpret you. 

Let’s add Instrumental!

I am eating watermelon with my sister.

You can use all those word orders and add this either at the beginning of the sentence, middle or last.

Example:

Ja jedem lubenicu sa mojom sestrom.

Jedem ja sa mojom sestrom lubenicu.

Sa mojom sestrom lubenicu ja jedem.

Ja sa mojom sestrom lubenicu jedem.

Sa mojom sestrom lubenicu jedem ja.

Jedem lubenicu ja sa mojom sestrom.

Now with Locative…

I am eating watermelon with my sister in the park.

Example:

Ja jedem lubenicu sa mojom sestrom u parku.

U parku jedem ja sa mojom sestrom lubenicu.

Sa mojom sestrom u parku lubenicu ja jedem.

Ja u parku sa mojom sestrom lubenicu jedem.

Sa mojom sestrom lubenicu jedem ja u parku.

U parku jedem lubenicu sa mojom sestrom.

Conclusion:

Some of these sentences sound unnatural, but you can still use them. That is why it's important to learn the Serbian cases. Once you learn them, you can use any variation of these word orders.